constness

src/server.js

@@ -351,7 +351,7 @@ function initializeExpressSync() {
     // upgrade handler
     httpServer.on('upgrade', function (req, socket, head) {
         // create a node response object for express
-        var res = new http.ServerResponse({});
+        const res = new http.ServerResponse({});
         res.assignSocket(socket);
 
         if (req.headers.upgrade === 'websocket') {