Custom Go Type with Marshallers

form.go

package form

import (
	"encoding/json"

	"gopkg.in/guregu/null.v4/zero"
)

type OptionalText string

func (s *OptionalText) MarshalJSON() ([]byte, error) {
	var z zero.String
	z.String = string(*s)
	return json.Marshal(z.String)
}

func (s *OptionalText) UnmarshalJSON(data []byte) error {
	text := string(data)
	*s = OptionalText(text)
	return nil
}