code: func DefaultDial(connectionTimeout time.Duration) func(network, addr string) (net.Conn, error) {
  	return func(network, addr string) (net.Conn, error) {
  		conn, err := net.DialTimeout(network, addr, connectionTimeout)
  		if err != nil {
  			return nil, err
  		}
  
  		// Heartbeating hasn't started yet, don't stall forever on a dead server.
  		// A deadline is set for TLS and AMQP handshaking. After AMQP is established,
  		// the deadline is cleared in openComplete.
  		if err := conn.SetDeadline(time.Now().Add(connectionTimeout)); err != nil {
  			return nil, err
  		}
  
  		return conn, nil
  	}
  }
docs: // DefaultDial establishes a connection when config.Dial is not provided