Golang File Descriptor Block Issue

main.go

package main

import (
	"fmt"
	"net"
	"log"
	"flag"
	"context"
	"syscall"
	"time"
)

var (
	listen = flag.String("listen", ":8000", "listen address")
	bug = flag.Bool("bug", true, "trigger bug")
	fix = flag.Bool("fix", false, "trigger fix")
)

func main() {
	flag.Parse()
	fmt.Println("Bug test with FD")

	ctx := context.Background()

	config := net.ListenConfig{}
	lis, err := config.Listen(ctx, "tcp", *listen)
	if err != nil {
		log.Fatal(err)
	}

	lisAddr := lis.Addr().String()
	fmt.Println("Listening", lisAddr)

	lisTcp := lis.(*net.TCPListener)

	f, err := lisTcp.File()
	if err != nil {
		log.Fatal(err)
	}

	if *bug {
		fd := f.Fd()
		fdi := int(fd)
		fmt.Println("FDI", fd, fdi)

		if *fix {
			syscall.SetNonblock(fdi, true)
		}
	}
	
	go func() {
		fmt.Println("Will close in 2 seconds")
		select {
		case <-time.After(time.Second*2):
			f.Close()
			fmt.Println("Trigger close")
			lis.Close()
		}
		fmt.Println("Close done")
	}()

	for {
		conn, err := lisTcp.AcceptTCP()
		if err != nil {
			log.Println("Error accepting", err)
			break
		}
		fmt.Println("Accepted connection", conn)
		conn.Write([]byte("Hello world!"))
		conn.Close()
	}
	fmt.Println("Done")
}