code: func (db *Database) Notify(channel string, payload ...string) error {
  	pl := strings.Join(payload, ",")
  	if len(pl) > 0 {
  		return db.Exec("SELECT pg_notify(?, ?)", channel, pl)
  	}
  	return db.Exec("NOTIFY " + handleIdentifier(channel))
  }
docs: // Notify sends a notification on channel, optional payloads are joined together and comma separated