exam guide · programming language

Go 1.26 practice questions and flashcards

A free course in the Go programming language, written from the language specification and the standard library documentation: 4,743 multiple-choice questions and 2,314 flashcards in 384 sets, from slices and maps to the scheduler and the garbage collector. Every code snippet was compiled and run against Go 1.26, and every question explains its answer.

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To begin with, three sets that need no account. Pick one and you are answering in seconds; your results stay in this browser.

Language · Slice headers: len, cap and the backing array · 18 questions
Concurrency · Unbuffered channels & synchronous handoff · 16 questions
Errors · Wrapping with %w, multiple %w & Unwrap · 17 questions

at a glance

Go version: Go 1.26 — every code snippet was compiled and run against it
Content: 4,743 questions and 2,314 flashcards in 384 sets
Areas: 10: Language · Generics · Concurrency · Errors · Standard library · Runtime · Performance · Testing · Tooling · Idioms
Question format: Multiple choice: four options, one correct, each with a worked explanation and links to the documentation behind it
Without an account: 30 sets — start one now; your results stay in this browser
With a free account: All 384 sets; your results are saved to your account
Price: Free
Official exam: None — the Go project runs no certification exam; this is wspell's own practice course

Try three questions

Sample questions from the sets that need no account, as the course asks them. Settle on an answer, then show the correct one.

From the set Slice headers: len, cap and the backing array
```
A batch worker hands a slice to a helper and prints the result afterwards:

func mutate(s []int) {
	s[0] = 99
	s = append(s, 4)
	s[1] = 88
}

func main() {
	s := make([]int, 3, 3)
	mutate(s)
	fmt.Println(s, len(s), cap(s))
}

What does main print?
```
1. [99 0 0] 3 3
2. [99 88 0] 3 3
3. [99 88 0 4] 4 4
4. [99 0 0 4] 4 3
Show the answer
Answer: A. [99 0 0] 3 3
The program prints [99 0 0] 3 3. A slice value is a three-word header — a pointer into a backing array, a length and a capacity — and it is passed to a function by value, like every other Go argument. s[0] = 99 writes through the shared pointer, so the caller sees it. Then append finds len == cap == 3, allocates a NEW backing array and stores the new header in the callee's own copy of s; s[1] = 88 writes into that new array, which the caller never sees. [99 88 0] 3 3 assumes the second write also lands in the caller's array, but the append moved the callee to different memory. [99 88 0 4] 4 4 and [99 0 0 4] 4 3 assume the caller's header is updated by the callee's append — it cannot be: the callee mutated a copy of the header, which is exactly why append's result must be assigned back by the caller.
Documentation
- Go spec — Slice types · go.dev
- Go blog — Go Slices: usage and internals · go.dev
From the set Unbuffered channels & synchronous handoff
```
A developer passes a value to themself through a channel, all inside one goroutine.

func main() {
	ch := make(chan string)
	ch <- "ping"
	fmt.Println(<-ch)
}

What happens when this runs on Go 1.26?
```
1. It prints ping, because an unbuffered channel still has room for one value
2. It stops at the send with the all-goroutines-asleep deadlock report
3. It panics at the send, because the channel has no receiver goroutine
4. It prints an empty line, because the receive yields the zero value
Show the answer
Answer: B. It stops at the send with the all-goroutines-asleep deadlock report
Verified on go1.26.4, 10/10 runs identical, exit status 2 and nothing on stdout:
fatal error: all goroutines are asleep - deadlock!
goroutine 1 [chan send]:
The trace points at the ch <- "ping" line.
The spec (Send statements): "A send on an unbuffered channel can proceed if a receiver is ready." The only goroutine is main, and it is the one stuck in the send, so the receive on the next line can never be reached. The runtime notices that no goroutine can ever run again and stops the program.
"It prints ping" treats the channel as having one free slot; make(chan string) has capacity zero, and "If the capacity is zero or absent, the channel is unbuffered and communication succeeds only when both a sender and receiver are ready" (spec, Channel types).
"It panics at the send" is wrong: blocking is the defined behaviour of the send, and what ends the program is the runtime's deadlock check, a fatal error rather than a panic.
"It prints an empty line" is wrong: execution never reaches the receive.
Documentation
- Go spec: Send statements · go.dev
- Go spec: Channel types · go.dev
From the set Wrapping with %w, multiple %w & Unwrap
```
var ErrClosed = errors.New("connection closed")

func main() {
	a := fmt.Errorf("send: %w", ErrClosed)
	b := fmt.Errorf("send: %v", ErrClosed)
	fmt.Println(a.Error() == b.Error())
	fmt.Println(errors.Is(a, ErrClosed), errors.Is(b, ErrClosed))
	fmt.Println(errors.Unwrap(a) == ErrClosed, errors.Unwrap(b))
}

What is printed (output lines separated by `/`)?
```
1. true / true false / true <nil>
2. false / true false / true <nil>
3. true / true true / true <nil>
4. true / true false / false <nil>
Show the answer
Answer: A. true / true false / true <nil>
It prints true, true false, true <nil>. The two messages are byte-for-byte identical - %w formats its operand exactly like %v - so nothing in the text tells you which one a caller can inspect. The difference is structural: %w records the operand, so the returned error has an Unwrap method that hands ErrClosed back, and errors.Is finds it. %v just interpolates the text, producing an ordinary error that wraps nothing, so errors.Is is false and errors.Unwrap returns nil. This is the single most consequential one-character choice in Go error handling, and it is invisible in logs - which is why an accidental %v shows up as 'errors.Is stopped matching' rather than as a formatting bug.
Documentation
- fmt.Errorf · pkg.go.dev
- Working with Errors in Go 1.13 · go.dev

Every set in the course

384 sets in 10 areas. The 30 that need no account start straight away; the rest need a free account.

Language — no account needed: 7 of 63

Source representation, lexical elements & semicolon insertion · 15 questions · free account
Numeric literals: integer, float, imaginary & digit separators · 14 questions · free account
Rune & string literals, escapes and raw strings · 16 questions · free account
Constants, untyped constants & default types · 19 questions · free account
iota, constant declarations & implicit repetition · 17 questions · free account
Constant expressions, representability & compile-time overflow · 15 questions · free account
Numeric types: sizes, overflow, shifts & integer division · 19 questions · free account
Arrays: value semantics, length in the type & comparability · 16 questions · free account
Slice headers: len, cap and the backing array · 18 questions
append, growth, aliasing & the three-index slice expression · 20 questions · free account
copy, clear & idiomatic slice insert/delete/filter · 16 questions · free account
Maps: semantics, comma-ok, delete & unordered iteration · 18 questions
Struct types: fields, tags, embedding syntax, comparability · 20 questions · free account
Struct layout: padding, alignment & field ordering · 14 questions · free account
Pointers, address operators & what is addressable · 16 questions · free account
Function types, function literals & closure capture · 19 questions · free account
Loop variable semantics: before and after Go 1.22 · 15 questions · free account
Interfaces: method sets, satisfaction & the empty interface · 18 questions
Value vs pointer receivers, method sets & addressability · 19 questions · free account
Type assertions, type switches & the comma-ok form · 16 questions · free account
Nil: nil interface vs typed-nil, nil maps/slices/channels/funcs · 16 questions · free account
Struct embedding, promotion, depth & shadowing · 18 questions · free account
Interface embedding, general interfaces & type sets · 14 questions · free account
Named types, aliases, underlying types & type identity · 18 questions · free account
Assignability & representability · 16 questions · free account
Conversions: numeric, string↔[]byte/[]rune, slice↔array · 18 questions · free account
Blocks, scope, shadowing & short variable declarations · 19 questions · free account
Operators, precedence & order of evaluation · 19 questions · free account
Comparison operators & comparability of every kind of value · 16 questions · free account
Composite literals, type elision & addressable composites · 14 questions · free account
Selectors, method expressions & method values · 16 questions · free account
Statements: if, switch, fallthrough, labeled break/continue/goto · 16 questions · free account
for statements & range over every rangeable operand · 18 questions · free account
range-over-func iterators, iter.Seq/Seq2 & the yield contract · 18 questions · free account
Assignment, tuple assignment, return & named result parameters · 16 questions · free account
Terminating statements & the missing-return rule · 12 questions · free account
defer: argument evaluation, LIFO order, loops & named results · 20 questions
panic, recover & what the runtime panics on · 20 questions · free account
Built-ins: len/cap/new/make/append/copy/clear/min/max/delete/close · 18 questions · free account
Packages, import declarations, import forms & exportedness · 14 questions · free account
Package initialization order, init() & program startup · 16 questions · free account
Strings, bytes, runes & UTF-8 correctness · 18 questions · free account
unsafe: Pointer rules, Sizeof/Alignof/Offsetof, Slice/String/Add · 18 questions · free account
Language versions, //go:build gating & the Go 1.25/1.26 language changes · 14 questions · free account
What does this print? — values, copies & aliasing · 18 questions
What does this print? — defer, panic & recover chains · 18 questions · free account
What does this print? — slices, append & shared backing arrays · 18 questions · free account
Find the bug — shadowing, scope & loop variables · 16 questions · free account
Does it compile? — assignability, method sets & type errors · 17 questions · free account
Spec vocabulary (flashcards) · 22 flashcards · free account
Keywords and what each one does (flashcards) · 25 flashcards · free account
Operators & punctuation reference (flashcards) · 29 flashcards · free account
Predeclared identifiers & built-in functions (flashcards) · 27 flashcards · free account
Types at a glance (flashcards) · 20 flashcards
Slice & map mental models (flashcards) · 18 flashcards · free account
Method sets & interface satisfaction rules (flashcards) · 20 flashcards · free account
Zero values & nil behaviours (flashcards) · 18 flashcards
defer / panic / recover rules (flashcards) · 16 flashcards · free account
Conversion & assignability rules (flashcards) · 20 flashcards · free account
Escape sequences, literal forms & UTF-8 facts (flashcards) · 18 flashcards · free account
unsafe & layout guarantees (flashcards) · 17 flashcards · free account
Compiler & vet messages decoded (flashcards) · 25 flashcards · free account
Spec section map (flashcards) · 23 flashcards · free account

Generics — no account needed: 2 of 19

Type parameter declarations on functions · 15 questions
Generic types, their methods & instantiation · 16 questions · free account
Constraint interfaces, type sets & unions · 18 questions · free account
Approximation elements (~T) & named-type constraints · 17 questions · free account
comparable, strict comparability & interface type arguments · 16 questions · free account
cmp.Ordered, the constraints packages & ordering helpers · 14 questions · free account
Type inference: function argument inference & constraint inference · 21 questions · free account
Inference beyond calls: assignment & conversion contexts · 18 questions · free account
Explicit instantiation & partial type arguments · 14 questions · free account
Operating on channels, maps & slices in generic code · 14 questions · free account
Self-referential and recursive constraints · 12 questions · free account
When NOT to use generics · 14 questions · free account
Generic data structures & algorithms in practice · 16 questions · free account
Generic code and performance: GCShape stenciling & dictionaries · 12 questions · free account
Does it compile? — constraint satisfaction & inference failures · 18 questions · free account
Terminology (flashcards) · 21 flashcards
Constraint library reference (flashcards) · 20 flashcards · free account
Type inference rules (flashcards) · 22 flashcards · free account
Generic stdlib APIs (flashcards) · 23 flashcards · free account

Concurrency — no account needed: 4 of 42

Goroutines: go statements, argument evaluation & lifetime · 18 questions
Unbuffered channels & synchronous handoff · 16 questions
Buffered channels: capacity, blocking, len & cap · 16 questions · free account
Closed channels: receive, send-panic & double-close · 16 questions · free account
Nil channels and their role in select · 14 questions · free account
Directional channel types & ownership conventions · 12 questions · free account
select: pseudo-random choice, default & blocking forever · 18 questions
range over a channel & the close contract · 14 questions · free account
sync.Mutex: semantics, non-reentrancy & copy hazards · 16 questions · free account
sync.RWMutex: when it helps, when it hurts, recursive-read deadlock · 14 questions · free account
sync.WaitGroup: Add placement, reuse & WaitGroup.Go (Go 1.25) · 16 questions · free account
sync.Once, OnceFunc, OnceValue & OnceValues · 16 questions · free account
sync.Cond: Wait/Signal/Broadcast & the loop-on-predicate rule · 14 questions · free account
sync.Pool: semantics, GC interaction & correct use · 14 questions · free account
sync.Map: when it wins, Load/Store/LoadOrStore/Range/Clear · 15 questions · free account
sync/atomic: typed atomics, CAS, Value & Pointer · 18 questions · free account
The Go memory model: happens-before & synchronisation edges · 18 questions · free account
Memory model corners: atomics, publication & double-checked locking · 16 questions · free account
Data races: what counts, what -race finds, benign-race myths · 16 questions · free account
context: cancellation, deadlines, propagation & Cause · 18 questions · free account
context values, key types & the request-scoped-only rule · 14 questions · free account
context misuse: stored in structs, ignored Done, leaked timers · 14 questions · free account
Deadlock patterns & "all goroutines are asleep" · 16 questions · free account
Goroutine leaks: causes, detection & the leak profile · 16 questions · free account
Worker pools & bounded parallelism · 16 questions · free account
Pipelines, fan-in/fan-out & explicit cancellation · 16 questions · free account
errgroup: WithContext, SetLimit & first-error semantics · 15 questions · free account
singleflight, semaphore & the x/sync toolbox · 13 questions · free account
Timers, tickers, time.After leaks & Go 1.23 timer changes · 14 questions · free account
Graceful shutdown & the lifecycle of a concurrent service · 14 questions · free account
Fix the race — diagnose and repair · 18 questions · free account
Find the deadlock — diagnose and repair · 16 questions · free account
What does this print? — ordering, select & channel timing · 18 questions · free account
Concurrency anti-patterns & "share memory by communicating" · 14 questions · free account
Primitives reference (flashcards) · 22 flashcards · free account
Channel behaviour truth table (flashcards) · 16 flashcards
sync & sync/atomic API (flashcards) · 24 flashcards · free account
context API & rules (flashcards) · 20 flashcards · free account
Memory model vocabulary (flashcards) · 20 flashcards · free account
Patterns catalogue (flashcards) · 20 flashcards · free account
Leak & deadlock signatures (flashcards) · 19 flashcards · free account
golang.org/x/sync toolbox (flashcards) · 12 flashcards · free account

Errors — no account needed: 3 of 14

The error interface, error values & construction · 16 questions
Sentinel errors: io.EOF, os.ErrNotExist & the sentinel contract · 16 questions · free account
Custom error types & when they earn their place · 16 questions · free account
Wrapping with %w, multiple %w & Unwrap · 17 questions
errors.Is: comparison, custom Is() methods & wrap chains · 16 questions · free account
errors.As, errors.AsType (Go 1.26) & target rules · 16 questions · free account
errors.Join, multi-errors & tree unwrapping · 14 questions · free account
panic vs error: when a panic is actually correct · 16 questions · free account
Error message style, context & not logging-then-returning · 14 questions · free account
Errors at API boundaries: opacity, stability & documentation · 14 questions · free account
Find the bug — error handling mistakes · 16 questions · free account
errors package API (flashcards) · 19 flashcards · free account
Stdlib sentinel errors you must know (flashcards) · 30 flashcards · free account
Error-handling vocabulary & rules (flashcards) · 18 flashcards

Standard library — no account needed: 5 of 122

fmt — verbs, flags, width & precision · 20 questions
fmt — Stringer, GoStringer, Formatter & recursion traps · 18 questions · free account
fmt — Sprintf vs Append*, Fprintf, Sscan family & Errorf · 16 questions · free account
strings — search, split, trim, replace & case · 20 questions
strings — Builder, Reader, Replacer, Cut & Split iterators · 18 questions · free account
bytes — Buffer, Reader & the mirror of strings · 18 questions · free account
strconv — Parse*, Format*, Append*, Quote & error shapes · 19 questions · free account
unicode & unicode/utf8 — runes, categories & decoding · 17 questions · free account
unicode/utf16, text/scanner & text/tabwriter · 15 questions · free account
slices — the generic slice toolbox · 24 questions · free account
maps & cmp — iteration, cloning & ordering helpers · 19 questions · free account
sort — the pre-generics API, sort.Interface & stability · 15 questions · free account
iter — Seq, Seq2, Pull, Pull2 & writing iterators · 18 questions · free account
io — Reader, Writer, Copy & the composition interfaces · 19 questions · free account
io — LimitReader, MultiReader/Writer, TeeReader, Pipe & SectionReader · 17 questions · free account
io/fs — FS interfaces, Sub, WalkDir, Glob & ReadLinkFS · 16 questions · free account
bufio — Reader, Writer, Scanner & buffer-size pitfalls · 19 questions · free account
os — files, permissions, Stat & error predicates · 21 questions · free account
os.Root — traversal-safe filesystem access · 14 questions · free account
os — environment, args, process, signals & exit semantics · 17 questions · free account
os/exec — Command, pipes, context, ExitError & injection safety · 19 questions · free account
path & path/filepath — cleaning, joining, globbing & separators · 18 questions · free account
embed — embed.FS, directive rules & what can be embedded · 14 questions · free account
time — Time, Duration, the monotonic clock & comparison · 18 questions · free account
time — layouts, formatting, parsing & locations · 17 questions · free account
time — Timer, Ticker, After, AfterFunc & the Go 1.23 changes · 16 questions · free account
math, math/bits & math/cmplx · 17 questions · free account
math/big — Int, Rat, Float & the receiver-as-destination convention · 16 questions · free account
math/rand vs math/rand/v2 — seeding, determinism & migration · 16 questions · free account
crypto/rand & secure randomness · 12 questions · free account
encoding/json — marshalling, struct tags, omitempty & omitzero · 20 questions
encoding/json — decoding into interfaces, numbers, streams & custom marshalers · 18 questions · free account
encoding/json/v2 & jsontext — the GOEXPERIMENT in Go 1.26 · 16 questions · free account
encoding/xml, encoding/csv & encoding/gob · 20 questions · free account
encoding/binary, hex, base32/base64, ascii85 & pem · 19 questions · free account
encoding/asn1 & the encoding marker interfaces · 14 questions · free account
regexp & regexp/syntax — RE2 semantics, submatches & performance · 20 questions · free account
net/http — client, Transport, timeouts & closing bodies · 20 questions · free account
net/http — server, Handler, and ServeMux routing (Go 1.22 patterns) · 19 questions
net/http — middleware, ResponseWriter, WriteHeader, flushing & hijacking · 17 questions · free account
net/http — cookies, redirects, CrossOriginProtection & request hardening · 18 questions · free account
net/http — HTTP/2, connection pooling & graceful shutdown · 15 questions · free account
net/http/httputil, httptrace, cgi & fcgi · 13 questions · free account
net — Dialer, Listener, Conn, deadlines & DNS · 19 questions · free account
net/netip, net/url & address parsing · 24 questions · free account
net/mail, net/smtp, net/textproto & net/rpc · 16 questions · free account
log & log/slog — handlers, attrs, groups, levels & context · 23 questions · free account
log/slog — custom handlers, LogValuer, MultiHandler & performance · 16 questions · free account
reflect — Type, Value, Kind & the three laws of reflection · 22 questions · free account
reflect — settability, struct tags, TypeAssert & iterator methods · 20 questions · free account
text/template — actions, pipelines, functions, scoping & errors · 18 questions · free account
html/template — contextual escaping and what it will not save you from · 17 questions · free account
database/sql — DB, pooling, Query/Exec, Scan & NULL handling · 21 questions · free account
database/sql — transactions, context, prepared statements & drivers · 17 questions · free account
crypto — hashing: md5/sha1/sha256/sha512/sha3, hash.Hash & HMAC · 19 questions · free account
crypto/cipher & crypto/aes — modes, AEAD, nonces & pitfalls · 19 questions · free account
crypto/tls — config, versions, certificates & verification · 18 questions · free account
crypto/x509 & pkix — parsing, pools, chains & verification · 18 questions · free account
crypto public key — rsa, ecdsa, ed25519, ecdh & crypto.Signer · 16 questions · free account
crypto — post-quantum & FIPS: mlkem, hpke, fips140, hkdf, pbkdf2 · 14 questions · free account
crypto/subtle & handling secrets in Go · 15 questions · free account
hash, hash/maphash, crc32/crc64/fnv/adler32 · 17 questions · free account
container/heap, container/list & container/ring · 15 questions · free account
compress/gzip, flate, zlib, bzip2 & lzw · 15 questions · free account
archive/tar & archive/zip · 15 questions · free account
mime, mime/multipart & quotedprintable · 15 questions · free account
image, image/color, image/draw & the codecs · 16 questions · free account
flag — definition, parsing, FlagSet & custom Values · 14 questions · free account
expvar, debug/buildinfo & build information · 14 questions · free account
go/token, go/ast, go/parser & go/printer · 20 questions · free account
go/types — type checking, Info & writing a static analyser · 17 questions · free account
go/constant, go/format, go/doc, go/build, go/version · 16 questions · free account
unique & weak — interning and weak pointers · 12 questions · free account
structs, plugin, syscall & the odd corners · 12 questions · free account
index/suffixarray, testing/quick & the rarely-taught packages · 10 questions · free account
debug/elf, macho, pe, dwarf, gosym & plan9obj · 12 questions · free account
simd/archsimd — the Go 1.26 experiment · 12 questions · free account
Deprecated & superseded APIs · 14 questions · free account
Pick the right package — API selection scenarios · 18 questions · free account
Find the bug — stdlib misuse · 18 questions · free account
What does this print? — fmt, time & strconv corners · 19 questions · free account
fmt verbs & flags (flashcards) · 30 flashcards · free account
strings API (flashcards) · 32 flashcards · free account
bytes API (flashcards) · 26 flashcards · free account
strconv API (flashcards) · 24 flashcards · free account
slices API (flashcards) · 28 flashcards · free account
maps, cmp & iter API (flashcards) · 20 flashcards · free account
sort API (flashcards) · 16 flashcards · free account
io & io/fs interfaces (flashcards) · 26 flashcards · free account
bufio API (flashcards) · 20 flashcards · free account
os & os.Root API (flashcards) · 30 flashcards · free account
os/exec & os/signal API (flashcards) · 18 flashcards · free account
path & path/filepath API (flashcards) · 22 flashcards · free account
time API & layout reference (flashcards) · 36 flashcards · free account
math, math/bits & math/big API (flashcards) · 31 flashcards · free account
math/rand/v2 & crypto/rand API (flashcards) · 16 flashcards · free account
encoding/json API & struct tag reference (flashcards) · 30 flashcards · free account
encoding/* other formats (flashcards) · 28 flashcards · free account
regexp API & RE2 syntax (flashcards) · 28 flashcards · free account
net/http server API (flashcards) · 29 flashcards · free account
net/http client & Transport API (flashcards) · 26 flashcards · free account
net, netip & net/url API (flashcards) · 26 flashcards · free account
log/slog API (flashcards) · 25 flashcards · free account
reflect API (flashcards) · 28 flashcards · free account
text/template & html/template reference (flashcards) · 30 flashcards · free account
database/sql API (flashcards) · 30 flashcards · free account
crypto hashing & HMAC API (flashcards) · 24 flashcards · free account
crypto/cipher, aes & AEAD (flashcards) · 20 flashcards · free account
crypto/tls & x509 API (flashcards) · 31 flashcards · free account
crypto public-key & post-quantum API (flashcards) · 26 flashcards · free account
hash & hash/maphash API (flashcards) · 18 flashcards · free account
container/* API (flashcards) · 18 flashcards · free account
compress & archive API (flashcards) · 23 flashcards · free account
mime & multipart API (flashcards) · 19 flashcards · free account
image API (flashcards) · 22 flashcards · free account
flag & expvar API (flashcards) · 23 flashcards · free account
go/* toolchain packages API (flashcards) · 29 flashcards · free account
unique, weak, structs & unsafe-adjacent (flashcards) · 15 flashcards · free account
debug/* & buildinfo (flashcards) · 18 flashcards · free account
Package map — which package holds what (flashcards) · 32 flashcards
Stdlib interfaces you must know (flashcards) · 25 flashcards · free account
Frozen, deprecated & superseded packages (flashcards) · 22 flashcards · free account

Runtime — no account needed: 2 of 23

The GMP scheduler: G, M, P, run queues & work stealing · 18 questions
Scheduling points, asynchronous preemption & tight loops · 16 questions · free account
Syscalls, handoff, sysmon & blocked threads · 14 questions · free account
GOMAXPROCS, container awareness (Go 1.25) & SetDefaultGOMAXPROCS · 15 questions · free account
Goroutine stacks: growth, copying, morestack & limits · 14 questions · free account
The garbage collector: tricolour marking & write barriers · 20 questions · free account
GC pacing: GOGC, GOMEMLIMIT & the GC guide · 20 questions · free account
Green Tea GC: Go 1.25 experiment, Go 1.26 default · 13 questions · free account
The memory allocator: size classes, mcache/mcentral/mheap, spans · 16 questions · free account
Map implementation: Swiss tables (Go 1.24) & what changed · 15 questions · free account
Slices, strings & interfaces in memory: headers, iface/eface & itab · 16 questions · free account
Finalizers, AddCleanup, weak pointers & object lifetime · 15 questions · free account
runtime package API: Gosched, NumGoroutine, Caller, Stack, ReadMemStats · 16 questions · free account
runtime/metrics, runtime/debug & the GODEBUG surface · 18 questions · free account
cgo at runtime: pointer-passing rules, cost & thread locking · 16 questions · free account
Panics, tracebacks & reading a crash dump · 18 questions · free account
Scheduler & GC traces: GODEBUG=schedtrace, gctrace, inittrace · 22 questions · free account
Scheduler vocabulary (flashcards) · 21 flashcards
GC vocabulary (flashcards) · 22 flashcards · free account
Memory layout & allocator terms (flashcards) · 20 flashcards · free account
GODEBUG & GOEXPERIMENT settings (flashcards) · 30 flashcards · free account
runtime & runtime/debug API (flashcards) · 29 flashcards · free account
Traceback & crash message decoder (flashcards) · 22 flashcards · free account

Performance — no account needed: 1 of 22

Escape analysis: what escapes and why · 18 questions
Reading -gcflags=-m and -m=2 output · 14 questions · free account
Reducing allocations: preallocation, reuse & zero-alloc paths · 18 questions · free account
Slice growth, preallocation & the real cost of append · 16 questions · free account
String building: concatenation, Builder, Appendf & conversions · 17 questions · free account
Map performance: sizing, key types & when not to use a map · 15 questions · free account
Inlining: the budget, what blocks it & how to check · 15 questions · free account
sync.Pool & object reuse — correct and incorrect · 15 questions · free account
Benchmarking method: b.Loop, ResetTimer, ReportAllocs, benchstat · 18 questions · free account
Benchmark pitfalls: dead-code elimination, noise & -count · 14 questions · free account
CPU & heap profiling with pprof · 20 questions · free account
Block, mutex, goroutine & leak profiles · 18 questions · free account
Execution traces, the trace viewer & the flight recorder · 17 questions · free account
Profile-guided optimisation (PGO) · 15 questions · free account
False sharing, cache lines, alignment & field ordering · 17 questions · free account
Concurrency performance: contention, sharding, atomics vs mutex · 18 questions · free account
Choosing the fast path — scenario selection · 17 questions · free account
Find the slow path — diagnose from a profile · 16 questions · free account
Escape analysis & inlining vocabulary (flashcards) · 20 flashcards · free account
pprof & trace tooling reference (flashcards) · 26 flashcards · free account
Benchmarking flags & testing API (flashcards) · 20 flashcards · free account
Cost model — what is cheap, what is not (flashcards) · 24 flashcards · free account

Testing — no account needed: 2 of 22

go test: flags, caching, package selection & exit behaviour · 19 questions · free account
testing.T basics: Error vs Fatal, Helper, Cleanup, TempDir, Setenv · 19 questions
Table-driven tests & subtests with t.Run · 18 questions
Parallel tests: t.Parallel, ordering & shared state · 16 questions · free account
TestMain, setup/teardown & package-level fixtures · 15 questions · free account
Benchmarks: testing.B, b.Loop (Go 1.24), b.N & reporting · 17 questions · free account
Fuzzing: f.Fuzz, seed corpus, corpus files & reproducing failures · 17 questions · free account
Example functions & Output comments · 13 questions · free account
Coverage: -cover, -coverprofile, modes & cross-package coverage · 14 questions · free account
testing/synctest — bubbles, virtual time & Wait · 17 questions · free account
net/http/httptest — Server, ResponseRecorder & TLS servers · 16 questions · free account
Golden files, testdata & update flags · 14 questions · free account
testing/fstest, iotest, quick, slogtest & cryptotest · 16 questions · free account
Test doubles in Go: interfaces, fakes & why not mocks · 14 questions · free account
Flaky tests: time, ordering, network & how to kill them · 14 questions · free account
testing.TB, shared helpers & assertions without a framework · 13 questions · free account
Integration tests, build tags, short mode & skipping · 16 questions · free account
Write the right test — scenario selection · 18 questions · free account
testing package API (flashcards) · 30 flashcards · free account
go test flag reference (flashcards) · 38 flashcards · free account
Test helper packages (flashcards) · 21 flashcards · free account
Testing vocabulary & conventions (flashcards) · 20 flashcards · free account

Tooling — no account needed: 1 of 32

Modules: go.mod directives and what each one means · 18 questions
go.sum, the checksum database, GOPRIVATE & GOFLAGS · 17 questions · free account
Semantic import versioning & /v2+ module paths · 16 questions · free account
Minimal version selection & the upgrade model · 16 questions · free account
go get, go mod tidy / why / graph / edit / vendor / download · 20 questions · free account
replace, exclude, retract & the ignore directive (Go 1.25) · 17 questions · free account
Workspaces: go work and multi-module development · 14 questions · free account
Toolchain lines, GOTOOLCHAIN & language version selection · 14 questions · free account
go build: flags, -ldflags, -trimpath, -tags & reproducibility · 21 questions · free account
Build constraints: //go:build syntax, file-name suffixes & precedence · 19 questions · free account
Cross-compilation: GOOS/GOARCH, GOARM/GOAMD64 & CGO_ENABLED · 17 questions · free account
cgo: directives, type mapping, pointer rules & build cost · 18 questions · free account
go generate, //go:generate & code generation practice · 16 questions · free account
go vet: the analyzer set and what each one catches · 20 questions · free account
gofmt, goimports, gofumpt & the formatting contract · 17 questions · free account
go doc, doc comments, links, lists & doc.go · 20 questions · free account
go fix and the modernizers (Go 1.26) · 16 questions · free account
go tool, the tool directive & dependency-pinned tools (Go 1.24) · 15 questions · free account
Environment: go env, GOFLAGS, GOCACHE, GOMODCACHE, GOPATH legacy · 17 questions · free account
GODEBUG, //go:debug & the Go 1 compatibility promise · 17 questions · free account
govulncheck & supply-chain hygiene · 16 questions · free account
Delve: breakpoints, goroutines & debugging a live process · 16 questions · free account
Compiler & linker directives: //go:noinline, //go:linkname, //go:embed, //go:nosplit · 15 questions · free account
Diagnosing a build — read the error, name the fix · 14 questions · free account
go command subcommand reference (flashcards) · 32 flashcards · free account
go.mod & go.work directive reference (flashcards) · 18 flashcards · free account
Environment variable reference (flashcards) · 32 flashcards · free account
Build constraint reference (flashcards) · 21 flashcards · free account
go vet analyzer reference (flashcards) · 35 flashcards · free account
Compiler & linker directive reference (flashcards) · 21 flashcards · free account
GODEBUG setting reference (flashcards) · 27 flashcards · free account
Module vocabulary (flashcards) · 26 flashcards · free account

Idioms — no account needed: 3 of 25

Naming: packages, variables, receivers, interfaces & getters · 20 questions
Package design: cohesion, size, cycles & internal/ · 18 questions · free account
Accept interfaces, return structs — and when not to · 17 questions · free account
Interface design: small, discovered not designed, no premature abstraction · 17 questions · free account
Zero-value-useful types & constructor design · 16 questions · free account
Composition over inheritance; embedding as a design tool · 16 questions · free account
Error-handling style: wrapping, context, and handling exactly once · 16 questions · free account
Doc comments: the convention, deprecation notices & examples · 16 questions · free account
Concurrency style: never start a goroutine without knowing how it stops · 16 questions · free account
API design & compatibility: additive change, options & variadic config · 17 questions · free account
Functional options, config structs & the builder trap · 16 questions · free account
Code Review Comments — the canonical list, part 1 · 18 questions · free account
Code Review Comments — the canonical list, part 2 · 21 questions · free account
Effective Go — the parts people skip · 19 questions · free account
Go proverbs — what each one actually means · 16 questions
Project layout, cmd/, internal/ & the "standard layout" myth · 15 questions · free account
Dependency hygiene: stdlib first, x/ packages, minimal dependencies · 14 questions · free account
Anti-patterns: util packages, any-soup, getters/setters, global state, init abuse · 16 questions · free account
Review this code — pick the idiomatic rewrite · 18 questions · free account
Go proverbs (flashcards) · 20 flashcards
Code Review Comments index (flashcards) · 31 flashcards · free account
Effective Go index (flashcards) · 26 flashcards · free account
Naming conventions (flashcards) · 20 flashcards · free account
Standard initialisms & Go's house vocabulary (flashcards) · 18 flashcards · free account
Design rules of thumb (flashcards) · 20 flashcards · free account

What is free

Every set is free. 30 of them need no account at all, so you can see what the course is like before you give anyone an email address; a free account opens the other 354.

Results you earn without an account stay in this browser. Create an account in the same browser and they are saved to it.

	Without an account	With a free account
Sets you can use	30 sets	all 384 sets
Your results	kept in this browser	saved to your account, on every device you sign in on
Price	free	free

Before this: A Tour of Go

A Tour of Go is the Go project's own interactive introduction to the language: modules of short lessons, each with code you can edit and run in the browser. If Go is new to you, start there.

This course comes after it. The tour teaches the language; these sets test whether you can predict what real code does — what it prints, where it blocks, when it panics — and say why, with the specification behind you.

A Tour of Go · go.dev

Prepare for it on wspell

Questions and flashcards on Go 1.26 — 30 sets need no account, the rest a free one.

frequently asked questions

Is the Go course free?

Yes. Every one of the 384 sets is free: 30 need no account at all, and a free account opens the other 354.

What does a free account add?

The other 354 sets, and your results saved to your account rather than to one browser, so they follow you to any device you sign in on. Results you earned here without an account are saved to it when you sign up in the same browser.

Which version of Go does it cover?

Go 1.26. Every code snippet was compiled and run against a Go 1.26 release, and the explanations quote the specification and the standard library documentation. Go 1.27, released in August 2026, is not covered yet.

How is it different from A Tour of Go?

The tour teaches you the language, lesson by lesson. This course tests it: short programs where you predict the output, find the deadlock or pick the right API, each followed by an explanation of why. Take the tour first if Go is new to you.

Is there an official Go certification?

No. The Go project does not run a certification exam, and this course is not connected to it. It is wspell's own practice material, written from the official documentation.

Can I use it on a phone?

Yes. It runs in the browser on a phone or a computer, and the code in the questions wraps to fit a small screen.

sources

The Go Programming Language Specification · go.dev
Go 1.26 Release Notes · go.dev
Go release history · go.dev
A Tour of Go · go.dev
Go brand and trademark usage guidelines · go.dev

about this guide

The questions, answers and explanations were written for wspell from the Go specification and the standard library documentation, and each answer links the documentation behind it.

Go changes with every release. This course was checked against Go 1.26; for anything that matters, the specification and the release notes on go.dev are the authority.

facts verified on September 28, 2026 against the sources above