code: func (ch *channel) delNick(nk *nick) {
  	if _, ok := ch.nicks[nk]; ok {
  		delete(ch.nicks, nk)
  		delete(ch.lookup, nk.nick)
  	} else {
  		logging.Warn("Channel.delNick(): %s not on %s.", nk.nick, ch.name)
  	}
  }
docs: // Disassociates a Nick from a Channel.