gistfile.go

package main

import (
	"encoding/json"
	"fmt"
)

type Response struct {
	Status    string      `json:"status"`
	Error     string      `json:"error"`
	ErrorCode string      `json:"error_code"`
	DebugInfo interface{} `json:"debug_info,omitempty"`
}

func main() {
	b, _ := json.Marshal(Response{})
	fmt.Printf("%s\n", b)

	var x *int
	res := Response{
		DebugInfo: x,
	}
	b, _ = json.Marshal(res)
	fmt.Printf("%s\n", b)
}

gistfile1.txt

{"status":"","error":"","error_code":""}
{"status":"","error":"","error_code":"","debug_info":null}