How to read JSON data that matches a struct in Go.

read_known_json.go

package main

import (
	"encoding/json"
	"fmt"
)

type User struct {
	Fname string
	Lname string
	Age   int
}

func main() {

	// Go stores JSON data as an array of bytes.
	jstr := `{"fname":"john","lname":"doe","age":25}`
	b := []byte(jstr)

	// If the incoming JSON data *matches* our struct, Go can directly
	// decode the JSON to our struct.
	// See https://blog.golang.org/json-and-go for the matching rules.
	var u User

	// Unmarshalling => decoding JSON to Go object.
	if err := json.Unmarshal(b, &u); err != nil {
		fmt.Println(err.Error())
	}

	fmt.Println(u.Fname)
}