message: backend: disable HTTP/2
  Our proxy can't handle WebSockets when using HTTP/2.
diff: @@ -524,6 +524,8 @@ func main() {
  httpsrv := &http.Server{
  Addr: listenURL.Host,
  Handler: srv.HTTPHandler(),
  + // Disable HTTP/2, which breaks WebSockets.
  + TLSNextProto: make(map[string]func(*http.Server, *tls.Conn, http.Handler)),
  }
  log.Infof("Binding to %s...", httpsrv.Addr)
  