Golang Cheatsheet

HTTP Handlers

package main
 
import (
	"encoding/json"
	"io"
	"net/http"
)
 
func main() {
	h := Handler{}
	
	mux := http.NewServeMux()
	mux.HandleFunc("POST /", h.Post)
	mux.HandleFunc("GET /{id}", h.Get)
 
	err := http.ListenAndServe(":8080", mux)
	if err != nil {
		panic(err)
	}
}
 
type Handler struct{}
 
func (h Handler) Post(w http.ResponseWriter, r *http.Request) {
	b, err := io.ReadAll(r.Body)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	
	var body PostBody
	if err := json.Unmarshal(b, &body); err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
 
	_, _ = w.Write(b)
}
 
func (h Handler) Get(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
 
	data := GetResponse{
		Name: id,
	}
 
	b, err := json.Marshal(data)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
 
	_, _ = w.Write(b)
}
 
type PostBody struct {
	Name string `json:"name"`
}
 
type GetResponse struct {
	Name string `json:"name"`
}
 

Json Marshal

data := Body{
    Name: id,
}
 
b, err := json.Marshal(data)

Json Unmarshal

body, _ := io.ReadAll(r.Body)
 
var data Request
err := json.Unmarshal(body, &data)

Pop from queue - first

x, a = a[0], a[1:]

Pop from stack - last

x, a = a[len(a)-1], a[:len(a)-1]

Push

a = append(a, x)

Copy

s1 := []int{1, 2, 3, 4, 5}
s2 := append([]int{}, s1...)
 
// or
 
s1 := []int{1, 2, 3, 4, 5}
s2 := make([]int, len(s1))
_ = copy(s2, s1) // s2 is now an independent copy of s1

Sync Package

WaitGroup - Go() or Add() and Done()
Map
Mutex
Close channel
For Select

for {
	select {
	case c <- x:
		x, y = y, x+y
	case <-quit:
		fmt.Println("quit")
		return
	}
	default:
		time.Sleep(50 * time.Millisecond)
}

// Create a type.
type Something string
 
// Create an alias.
type Something = string

go clean -cache -testcache
go tool cover -html=coverage.txt
go test -v -count=1 -race -p 1 -shuffle=on ./...
go test -v -count=1 -shuffle=on -coverprofile=coverage.out -tags "unit integration" ./...