Write header before sending data

web/server.go

@@ -152,6 +152,7 @@ func (s *Server) HandlerAttemptStream(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Access-Control-Allow-Origin", "*")
 	id, ch := s.addAttemptListener()
 	defer s.closeAttemptListener(id)
+	w.WriteHeader(http.StatusOK)
 
 	flusher := w.(http.Flusher)
 	ticker := time.NewTicker(30 * time.Second)