Go Quick Reference

package main

import "fmt"

func main() {
    fmt.Println("Hello")
}

var count int = 10

name := "Ada"  // short declaration

const Max = 100

a, b := 1, 2

fmt.Printf("%s is %d\n", name, age)

fmt.Sprintf("%.2f", price)

strconv.Itoa(42)

n, err := strconv.Atoi("42")

float64(n)

nums := []int{3, 1, 2}

nums = append(nums, 4)

buf := make([]byte, 0, 1024)

nums[1:3]

for i, n := range nums {
    fmt.Println(i, n)
}

slices.Sort(nums)

sort.Slice(users, func(i, j int) bool { return users[i].Age < users[j].Age })

slices.Contains(nums, 3)

slices.Reverse(nums)

ages := map[string]int{"Ada": 36}
ages["Bob"] = 40

age, ok := ages["Ada"]

delete(ages, "Bob")

if err := run(); err != nil {
    return err
}

for i := 0; i < 5; i++ { }

for running { }

for { }  // forever

for i := range 10 { }

switch day {
case "sat", "sun":
    fmt.Println("weekend")
default:
    fmt.Println("weekday")
}

f, _ := os.Open(name)
defer f.Close()

func divide(a, b float64) (float64, error) {
    if b == 0 {
        return 0, errors.New("divide by zero")
    }
    return a / b, nil
}

type User struct {
    Name string
    Age  int
}
u := User{Name: "Ada", Age: 36}

func (u User) Greet() string {
    return "Hi " + u.Name
}

func (u *User) Birthday() { u.Age++ }

type Shape interface {
    Area() float64
}

func Map[T, U any](xs []T, f func(T) U) []U { }

type User struct {
    Name string `json:"name"`
}

data, err := os.ReadFile("in.txt")
if err != nil {
    log.Fatal(err)
}

return fmt.Errorf("loading config: %w", err)

errors.Is(err, os.ErrNotExist)

errors.As(err, &target)

go doWork()

ch := make(chan int)
go func() { ch <- 42 }()
v := <-ch

var wg sync.WaitGroup
wg.Add(1)
go func() {
    defer wg.Done()
    work()
}()
wg.Wait()

select {
case msg := <-ch:
    fmt.Println(msg)
case <-time.After(time.Second):
    fmt.Println("timeout")
}

go mod init example.com/app

go run .

go build -o app .

go test ./...

go test -run TestName -v

go get github.com/gin-gonic/gin

go mod tidy

go fmt ./...

go vet ./...