Go behaves weirdly with int64 being marshalled out of interfaces

int64.go

package main

import (
	"fmt"
	"encoding/json"
)

type Data map[string]interface{}

func main() {
	var data Data
	body := []byte("{\"id\":4418489049307132905}")
	if err := json.Unmarshal(body, &data); err != nil {
        	panic(err)
    	}
	tag_id := data["id"].(int64)
	fmt.Println(tag_id)
}