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Go Cheat Sheet — Syntax and Standard Library Reference

Go is small on purpose. This sheet covers nearly all of the everyday syntax, plus the go command and the concurrency basics.

Put it into practice with the matching tool.

Generate Go structs from JSON →

Variables and types

x := 42Declare and infer type (inside functions)

var name string = "Ana"Explicit declaration

const Pi = 3.14Constant

int int64 float64 string bool byte runeCommon built-in types

float64(x)Type conversion — always explicit

Zero values: 0, "", false, nilWhat uninitialised variables hold

Slices and maps

xs := []int{1, 2, 3}Slice literal

xs = append(xs, 4)Append — always reassign the result

xs[1:3]Sub-slice (shares the underlying array)

make([]int, 0, 10)Slice with length 0 and capacity 10

m := map[string]int{"a": 1}Map literal

v, ok := m["k"]Look up and check whether the key exists

delete(m, "k")Remove a key

Control flow

for i := 0; i < n; i++ { }Classic loop

for i, v := range xs { }Iterate a slice, map, string, or channel

for i := range 10 { }Loop 0–9 (Go 1.22+)

for cond { }While loop

if v, err := f(); err != nil { }If with an init statement

switch x { case 1, 2: ... default: ... }Switch — no fallthrough by default

defer f.Close()Run when the surrounding function returns

Functions and errors

func add(a, b int) int { }Function with typed parameters

func f() (int, error) { }Multiple return values

if err != nil { return err }The standard error check

fmt.Errorf("load: %w", err)Wrap an error with context

errors.Is(err, os.ErrNotExist)Check for a wrapped error

func sum(nums ...int) intVariadic function

Structs and interfaces

type User struct { Name string `json:"name"` }Struct with a JSON tag

func (u *User) Rename(n string) { }Method with a pointer receiver

type Shape interface { Area() float64 }Interface — satisfied implicitly

v, ok := x.(string)Type assertion

func Map[T, U any](xs []T, f func(T) U) []UGeneric function

Concurrency and the go tool

go f()Start a goroutine

ch := make(chan int); ch <- 1; v := <-chCreate, send on, and receive from a channel

select { case v := <-ch: ... }Wait on several channel operations

var wg sync.WaitGroupWait for a group of goroutines

go mod init example.com/appStart a module

go run . / go build / go test ./...Run, build, and test

go fmt ./... / go vet ./...Format code / report suspicious constructs

Related guides

Typing API Responses: From JSON to TypeScript Types

More cheat sheets

Regex →Markdown →SQL →JS Arrays →TypeScript →JS Strings →