Example of using https://github.com/campoy/jsonenums

main.go

package main

//go:generate jsonenums -type=Status
type Status int

const (
	Pending Status = iota
	Sent
	Received
	Rejected
)

func main() {
	status := Received
	data, err := status.MarshalJSON()
	if err != nil {
		panic(err)
	}

	statusCopy := new(Status)
	err = statusCopy.UnmarshalJSON(data)
	if err != nil {
		panic(err)
	}
}

status_jsonenums.go

// generated by jsonenums -type=Status; DO NOT EDIT

package main

import (
	"encoding/json"
	"fmt"
)

var (
	_StatusNameToValue = map[string]Status{
		"Pending":  Pending,
		"Sent":     Sent,
		"Received": Received,
		"Rejected": Rejected,
	}

	_StatusValueToName = map[Status]string{
		Pending:  "Pending",
		Sent:     "Sent",
		Received: "Received",
		Rejected: "Rejected",
	}
)

func init() {
	var v Status
	if _, ok := interface{}(v).(fmt.Stringer); ok {
		_StatusNameToValue = map[string]Status{
			interface{}(Pending).(fmt.Stringer).String():  Pending,
			interface{}(Sent).(fmt.Stringer).String():     Sent,
			interface{}(Received).(fmt.Stringer).String(): Received,
			interface{}(Rejected).(fmt.Stringer).String(): Rejected,
		}
	}
}

// MarshalJSON is generated so Status satisfies json.Marshaler.
func (r Status) MarshalJSON() ([]byte, error) {
	if s, ok := interface{}(r).(fmt.Stringer); ok {
		return json.Marshal(s.String())
	}
	s, ok := _StatusValueToName[r]
	if !ok {
		return nil, fmt.Errorf("invalid Status: %d", r)
	}
	return json.Marshal(s)
}

// UnmarshalJSON is generated so Status satisfies json.Unmarshaler.
func (r *Status) UnmarshalJSON(data []byte) error {
	var s string
	if err := json.Unmarshal(data, &s); err != nil {
		return fmt.Errorf("Status should be a string, got %s", data)
	}
	v, ok := _StatusNameToValue[s]
	if !ok {
		return fmt.Errorf("invalid Status %q", s)
	}
	*r = v
	return nil
}