How to get file descriptor from NetConn for EPOLL handling?

[StarpTech]

Hi, as titled. We are trying to get the raw TCP connection to read the file descriptor.

netConn := websocket.NetConn(reqCtx.Context(), wsConn, websocket.MessageText)

We want to use this library in combination with https://github.com/smallnest/epoller

[StarpTech]

Our workaround

	var netConn net.Conn

	clientTrace := &httptrace.ClientTrace{
		GotConn: func(info httptrace.GotConnInfo) {
			netConn = info.Conn
		},
	}
	clientTraceCtx := httptrace.WithClientTrace(requestContext, clientTrace)
	conn, upgradeResponse, err := websocket.Dial(clientTraceCtx, options.URL, &websocket.DialOptions{
		HTTPClient:      c.httpClient,
		HTTPHeader:      options.Header,
		CompressionMode: websocket.CompressionDisabled,
		Subprotocols:    subProtocols,
	})
	if err != nil {
		return nil, err
	}

[mafredri]

Thanks for sharing your workaround @StarpTech! We'll think about the API but surely we can expose an easier way to grab the raw net.Conn.

Somewhat related: #331

[StarpTech]

@mafredri thanks and that would be great!