How to Marshal/Unmarshal Enums in JSON in Go

Go enums (defined as type aliases for int or string) marshal and unmarshal as their underlying type by default, so no special code is required. Use encoding/json directly on the enum value or a struct containing it.

package main

import (
	"encoding/json"
	"fmt"
)

type Status int

const (
	StatusPending Status = iota
	StatusActive
	StatusClosed
)

type Task struct {
	Name   string
	Status Status
}

func main() {
	task := Task{Name: "Deploy", Status: StatusActive}
	b, _ := json.Marshal(task)
	fmt.Println(string(b)) // {"Name":"Deploy","Status":1}

	var t Task
	json.Unmarshal(b, &t)
	fmt.Println(t.Status) // 1
}

If you need string values (e.g., "active") instead of numbers, implement MarshalJSON and UnmarshalJSON on the enum type to convert between the string and the underlying integer.

Go enums are just numbers or strings in disguise, so the JSON library treats them exactly like regular numbers or strings. You don't need to do anything special to save or load them; they just work out of the box. Think of it like saving a temperature reading: the computer just saves the number, not the label you gave it.