You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: demo_15.go
    path of file: ./repos/Go/00-基础语法/codes
    
    the code of the file until where you have to start completion: //demo_15.go
package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	res := make(map[s
    
func main() {
	res := make(map[string]interface{})
	res["code"] = 200
	res["msg"]  = "success"
	res["data"] = map[string]interface{}{
		"username" : "Tom",
		"age"      : "30",
		"hobby"    : []string{"读书","爬山"},
	}
	fmt.Println("map data :", res)

	//序列化
	jsons, errs := json.Marshal(res)
	if errs != nil {
		fmt.Println("json marshal error:", errs)
	}
	fmt.Println("")
	fmt.Println("--- map to json ---")
	fmt.Println("json data :", string(jsons))

	//反序列化
	res2 := make(map[string]interface{})
	errs = json.Unmarshal([]byte(jsons), &res2)
	if errs != nil {
		fmt.Println("json marshal error:", errs)
	}
	fmt.Println("")
	fmt.Println("--- json to map ---")
	fmt.Println("map data :", res2)
}