package telegram type Message struct { MessageID int `json:"message_id"` From User `json:"from"` Date int `json:"date"` Text *string `json:"text"` Chat *Chat `json:"chat"` MediaGroupID *string `json:"media_group_id"` Photo []PhotoSize `json:"photo"` Caption *string `json:"caption"` } func (m Message) GetMaxPhotoFileID() string { var fileSize int64 var photoSize PhotoSize for _, p := range m.Photo { if p.FileSize > fileSize { photoSize = p } } return photoSize.FileID }