def find(nick)
      if nick == @bot.nick
        return @bot
      end

      downcased_nick = nick.irc_downcase(@bot.irc.isupport["CASEMAPPING"])
      @mutex.synchronize do
        return @cache[downcased_nick]
      end
    end
def find(nick)
      if nick == @bot.nick
        return @bot
      end

      downcased_nick = nick.irc_downcase(@bot.irc.isupport["CASEMAPPING"])
      @mutex.synchronize do
        return @cache[downcased_nick]
      end
    end
Finds a user.

 @param [String] nick nick of a user
 @return [User, nil]