code: func (m *LocationMessage) MarshalJSON() ([]byte, error) {
  	return json.Marshal(&struct {
  		Type       MessageType      `json:"type"`
  		Title      string           `json:"title"`
  		Address    string           `json:"address"`
  		Latitude   float64          `json:"latitude"`
  		Longitude  float64          `json:"longitude"`
  		QuickReply *QuickReplyItems `json:"quickReply,omitempty"`
  	}{
  		Type:       MessageTypeLocation,
  		Title:      m.Title,
  		Address:    m.Address,
  		Latitude:   m.Latitude,
  		Longitude:  m.Longitude,
  		QuickReply: m.quickReplyitems,
  	})
  }
docs: // MarshalJSON method of LocationMessage