Go MGO custom time struct

time.go

type BaseFields struct {
	ID        string    `json:"id" bson:"_id"`
	CreatedAt time.Time `json:"created_at" bson:"created_at"`
	UpdatedAt time.Time `json:"updated_at" bson:"updated_at"`
	DeletedAt DeletedAt `json:"deleted" bson:"deleted_at,omitempty"`
}

type DeletedAt struct {
	time.Time `bson:",omitempty"`
}

func GetDeletedAt() (t DeletedAt) {
	t.Time = time.Now()
	return
}

func (doc DeletedAt) MarshalJSON() ([]byte, error) {
	res := "true"
	if doc.IsZero() {
		res = "false"
	}
	return []byte(res), nil
}

func (doc *DeletedAt) UnmarshalJSON(data []byte) error {
	if string(data) == "true" {
		t := GetDeletedAt()
		doc = &t
	} else {
		doc = &DeletedAt{}
	}
	return nil
}