code: func (o *ClientOptions) AddBroker(server string) *ClientOptions {
  	if len(server) > 0 && server[0] == ':' {
  		server = "127.0.0.1" + server
  	}
  	if !strings.Contains(server, "://") {
  		server = "tcp://" + server
  	}
  	brokerURI, err := url.Parse(server)
  	if err != nil {
  		ERROR.Println(CLI, "Failed to parse %q broker address: %s", server, err)
  		return o
  	}
  	o.Servers = append(o.Servers, brokerURI)
  	return o
  }
docs: // AddBroker adds a broker URI to the list of brokers to be used. The format should be
  // scheme://host:port
  // Where "scheme" is one of "tcp", "ssl", or "ws", "host" is the ip-address (or hostname)
  // and "port" is the port on which the broker is accepting connections.
  //
  // Default values for hostname is "127.0.0.1", for schema is "tcp://".
  //
  // An example broker URI would look like: tcp://foobar.com:1883