json.go

package main

import (
	"encoding/json"
	"errors"
	"log"
	"net/http"
)

/*

This code won't work, because it's not hitting a real API,
but pretend that the API returns this JSON response:

GET /users/123

{
	"id": 123,
	"first_name": "John",
	"last_name": "Doe"
}

*/

func getJSON(endpoint string, val interface{}) error {
	resp, err := http.Get("https://myapi.com/" + endpoint)
	if err != nil {
		return err
	}
	
	// Close the response body when this function returns.
	defer resp.Body.Close()
	
	if resp.StatusCode != http.StatusOK {
		return errors.New("api: non-200 response code")
	}
	dec := json.NewDecoder(resp.Body)
	return dec.Decode(val)
}

type User struct {
	FirstName string `json:"first_name"`
	LastName  string `json:"last_name"`
	ID        int    `json:"id"`
}

func main() {
	var user User
	if err := getJSON("users/123", &user); err != nil {
		log.Fatal(err)
	}

	log.Printf("Hello, %s!", user.FirstName)
}