Function dial

dial.go:124–186

(ctx context.Context, urls string, opts *DialOptions, rand io.Reader)

}

func dial(ctx context.Context, urls string, opts *DialOptions, rand io.Reader) (_ *Conn, _ *http.Response, err error) {
	defer errd.Wrap(&err, "failed to WebSocket dial")

	var cancel context.CancelFunc
	ctx, cancel, opts = opts.cloneWithDefaults(ctx)
	if cancel != nil {
		defer cancel()
	}

	secWebSocketKey, err := secWebSocketKey(rand)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to generate Sec-WebSocket-Key: %w", err)
	}

	var copts *compressionOptions
	if opts.CompressionMode != CompressionDisabled {
		copts = opts.CompressionMode.opts()
	}

	resp, err := handshakeRequest(ctx, urls, opts, copts, secWebSocketKey)
	if err != nil {
		return nil, resp, err
	}
	respBody := resp.Body
	resp.Body = nil
	defer func() {
		if err != nil {
			// We read a bit of the body for easier debugging.
			r := io.LimitReader(respBody, 1024)

			timer := time.AfterFunc(time.Second*3, func() {
				respBody.Close()
			})
			defer timer.Stop()

			b, _ := io.ReadAll(r)
			respBody.Close()
			resp.Body = io.NopCloser(bytes.NewReader(b))
		}
	}()

	copts, err = verifyServerResponse(opts, copts, secWebSocketKey, resp)
	if err != nil {
		return nil, resp, err
	}

	rwc, ok := respBody.(io.ReadWriteCloser)
	if !ok {
		return nil, resp, fmt.Errorf("response body is not a io.ReadWriteCloser: %T", respBody)
	}

	return newConn(connConfig{
		subprotocol:    resp.Header.Get("Sec-WebSocket-Protocol"),
		rwc:            rwc,
		client:         true,
		copts:          copts,
		flateThreshold: opts.CompressionThreshold,
		onPingReceived: opts.OnPingReceived,