code: func (c *Callbacks) OnCMsgGCToClientTournamentItemDrop(fn func(*dota.CMsgGCToClientTournamentItemDrop) error) {
  	c.onCMsgGCToClientTournamentItemDrop = append(c.onCMsgGCToClientTournamentItemDrop, fn)
  }
docs: // OnCMsgGCToClientTournamentItemDrop registers a callback for EDotaUserMessages_DOTA_UM_TournamentDrop