code: func (c *Callbacks) OnCDOTAUserMsg_ReceivedXmasGift(fn func(*dota.CDOTAUserMsg_ReceivedXmasGift) error) {
  	c.onCDOTAUserMsg_ReceivedXmasGift = append(c.onCDOTAUserMsg_ReceivedXmasGift, fn)
  }
docs: // OnCDOTAUserMsg_ReceivedXmasGift registers a callback for EDotaUserMessages_DOTA_UM_ReceivedXmasGift