package main

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

type jsonDecodeHandler int

type User struct {
	Firstname string `json:"firstname"`
	Lastname  string `json:"lastname"`
	Age       int    `json:"age"`
}

func (jsonHandler jsonDecodeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	var user User
	json.NewDecoder(r.Body).Decode(&user)
	fmt.Fprintf(w, "%s %s is %d years old!", user.Firstname, user.Lastname, user.Age)
}

func main() {
	var dec jsonDecodeHandler
	http.ListenAndServe("localhost:8080", dec)
}