big int marshal-unmarshal

package main

import (
	"fmt"
	"encoding/json"
	"math/big"
	"os"
)

type dc struct {
	IP IP
	Name string
}

type IP struct { 
	big.Int
}

func (ip *IP) MarshalJSON() ([]byte, error) {
	res := fmt.Sprintf("%x", ip)
	fmt.Println("Marshaling into ", res)	
	return json.Marshal(res)
}

func (ip *IP) UnmarshalJSON(b []byte) error {
	var val string
	err := json.Unmarshal(b, &val)
	if err != nil {
		panic(err)
	}
	
	ip.SetString(val, 16)
	
	return nil
}

func main() {
	d := new(IP)
	d.SetString("fec0dead00000000", 16)
	
	DC := new(dc)
	DC.Name = "Test"
	DC.IP = *d
	
	j, err := json.Marshal(DC)
	if err != nil {
		fmt.Println("Error: ", err)
	}
	
	fmt.Printf("Hello, playground: %x \n", d)
	os.Stdout.Write(j)
	
	var NewDc dc
	err = json.Unmarshal(j, &NewDc)
	if err != nil {
		panic(err)
	}
	
	fmt.Printf("\n\n Unmarshalled as: %v, %s", NewDc, NewDc.IP.Int.Text(16))
}


// https://play.golang.org/p/dyHG0E_yrd