If listener.Accept returns an error then the server stops responding

[stefanba3]

For example, here:

func (s *server) run() {
	defer s.wg.Done()
	for {
		client, err := s.netListener.Accept()
		if err != nil {
			break
		}

		s.handle(client)
	}
}

netListener is commonly a TLS listener, which can return an error from Accept for many reasons. Breaking out of the loop stops the server from accepting new connections. And, as far as I can tell, there is no way to know from the outside (since run gets called in a goroutine) that this has happened.

[stefanba3]

Actually, I am wrong. TLS wont return handshake errors from Accept. So this issue is less serious than I thought. I don't know if we can assume Accept will only return an error if closed, so it might still be a good idea to guard against that case.

[andrewkroh]

I think this code could use errors.Is(err, net.ErrClosed) to determine if the loop should break. Other errors should probably be logged, but continue to Accept().

net.ErrClosed is newly exported in Go 1.16. golang/go#4373 (comment)