func Listen(network, addr string) (net.Listener, error) {
	ln, err := cfg.NewListener(network, addr)
	if err != nil && strings.Contains(err.Error(), "SO_REUSEPORT") {
		return nil, &ErrNoReusePort{err}
	}
	return ln, err
}
func Listen(network, addr string) (net.Listener, error) {
	ln, err := cfg.NewListener(network, addr)
	if err != nil && strings.Contains(err.Error(), "SO_REUSEPORT") {
		return nil, &ErrNoReusePort{err}
	}
	return ln, err
}
// Listen returns TCP listener with SO_REUSEPORT option set.
//
// The returned listener tries enabling the following TCP options, which usually
// have positive impact on performance:
//
// - TCP_DEFER_ACCEPT. This option expects that the server reads from accepted
//   connections before writing to them.
//
// - TCP_FASTOPEN. See https://lwn.net/Articles/508865/ for details.
//
// Use https://github.com/valyala/tcplisten if you want customizing
// these options.
//
// Only tcp4 and tcp6 networks are supported.
//
// ErrNoReusePort error is returned if the system doesn't support SO_REUSEPORT.