[golang] json 사용

package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"time"
)

type User struct {
	FirstName string    `json:"first_name"`
	LastName  string    `json:"last_name"`
	Email     string    `json:"email"`
	CreatedAt time.Time `json:"created_at"`
}

type fooHandler struct{}

func (f *fooHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	user := new(User)
	err := json.NewDecoder(r.Body).Decode(user)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		fmt.Fprint(w, err)
		return
	}
	user.CreatedAt = time.Now()
	data, _ := json.Marshal(user)
	w.Header().Add("content-type", "application/json")
	w.WriteHeader(http.StatusOK)
	fmt.Fprintf(w, string(data))
}

func barHandler(w http.ResponseWriter, r *http.Request) {
	name := r.URL.Query().Get("name")
	if name == "" {
		name = "World"
	}
	fmt.Fprintf(w, "Hello %s!", name)
}

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprint(w, "Hello world")
	})
	mux.HandleFunc("/bar", barHandler)
	mux.Handle("/foo", &fooHandler{})
	http.ListenAndServe(":3000", mux)
}

json.NewDecoder(r.Body).Decode(user) :: r.Body를 읽어서 user형태로 디코딩 처리
json.Marshal(user) :: user타입 데이터를 byte[]와 error로 변환
string(data) :: byte[]로 변환된 데이터를 String타입으로 형변환

참고 :: https://www.youtube.com/watch?v=vOW0j6hd-Rg&list=PLy-g2fnSzUTDALoERcKDniql16SAaQYHF&index=2