Migrate valyala/tcplisten to this repo #1926

[ksw2000]

Resolve #1926

This PR moves the valyala/tcplisten package to fasthttp and also migrates PR#6 and PR#10 together. Additionally, it upgrades the deprecated ioutil package and replaces the +build directive with go:build. Furthermore, it fixes the warning in tcplisten_test.go regarding "the goroutine calls T.Fatalf, which must be called in the same goroutine as the test".

[ksw2000]

I think the error is caused by DeferAccept and FastOpen not being implemented in darwin 🤔

[gaby]

@ksw2000 Can these be added too?

• z/OS Compatibility tcplisten#8
• Add TCP keepalive support? tcplisten#3

[ksw2000]

@gaby

@ksw2000 Can these be added too?

• z/OS Compatibility tcplisten#8
• Add TCP keepalive support? tcplisten#3

About implementation of the keepalive feature:

When calling NewListener for tcplisten.Config, it internally calls net.FileListener to generate a net.Listener struct/interface, which contains the private field lc net.ListenConfig. I don't have a graceful solution to implement keepalive at the moment.

However, there is an alternative method to set keepAlive after calling ln.Accept().

func main() {
	cfg := tcplisten.Config{
		ReusePort: true,
	}
	ln, err := cfg.NewListener("tcp", "0.0.0.0:8082")
	if err != nil {
		panic(err)
	}
	for {
		conn, err := ln.Accept()
		if err != nil {
			panic(err)
		}
		if conn, ok := conn.(*net.TCPConn); ok {
			conn.SetKeepAlive(true)
			conn.SetKeepAlivePeriod(time.Second)
		}
		go func() {
			defer conn.Close()
			fmt.Println("Accepted connection from", conn.RemoteAddr())
		}()
	}
}

Of course, if we still want to add the keepAlive feature, we could also wrap the net.Listener generated by net.FileListener and override the Accept() method, set keepalive before returning conn. But, in my opinion, this approach might confuse the original usage patterns.

[gaby]

@ksw2000 Agree, it does sound confusing.