What version of Go are you using (go version)?

$ go version
1.13.7

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

Windows 64 bit

$ go env

What did you do?

Pre issue we created a single listener for http and use that to Listen with protocol = tcp

listener    net.Listener
func (this *HttpEndpoint) Listen() error {
	ln, err := net.Listen("tcp", this.httpAddr)
	if err == nil {
		this.listener = ln
		srv := &http.Server{
			Handler:           this.mux,
			ReadHeaderTimeout: 5 * time.Second,
		}
		go srv.Serve(ln)
		logging.Infop("HttpEndpoint: Listen", logging.Pair{"Address", ln.Addr()})
	}
	return err
}

Then we changed the code to use tcp4 and/or tcp6 explicitly in the Listen function. The code for this is given below.

1. If server sends us ipv6=true, then we should
   (1) start listening to ipv6 - fail service if listen fails
   (2) try to listen to ipv4 - don't fail service even if listen fails.
2. If server sends us ipv6=false, then we should
   (1) start listening to ipv4 - fail service if listen fails
   (2) try to listen to ipv6 - don't fail service even if listen fails.

Create 2 listeners - one for http and one for https.
Code to create the listeners -

listener      []net.Listener

func getNetwProtocol() []string {
	if server.IsIPv6() {
		return []string{"tcp6", "tcp4"}
	}
	return []string{"tcp4", "tcp6"}
}

func (this *HttpEndpoint) Listen() error {

	srv := &http.Server{
		Handler:           this.mux,
		ReadHeaderTimeout: 5 * time.Second,
	}

	for i, netW := range getNetwProtocol() {
		ln, err := net.Listen(netW, this.httpAddr)

		if err != nil {
			if i == 0 {
				return fmt.Errorf("Failed to start service: %v", err.Error())
			} else {
				logging.Infof("Failed to start service: %v", err.Error())
			}
		} else {
			this.listener = append(this.listener, ln)
			go srv.Serve(ln)
			logging.Infop("HttpEndpoint: Listen", logging.Pair{"Address", ln.Addr()})
		}
	}

	return nil
}

What did you expect to see?

No change in performance tests (this is true for the Linux - Centos7 machine and Mac)
Previous throughput - 131K

What did you see instead?

Slowdown only on the Windows performance tests. The throughput on Linux and Mac more or less stayed the same.
On windows we saw a 50% degradation.

I changed the code to test just using tcp and tcp4/tcp6 with the rest of the code being the same. Thats when I see the degradation in performance.

Question - Why is there an performance issue with using tcp4/tcp6 instead of tcp in net.Listen() on Windows ? Is this an expected issue ?