changed middleware order to allow preflight

app.js

@@ -43,12 +43,22 @@ let root = {
 };
 
 let app = express();
+
+/* leaving this here for reference
+app.options('/graphql', function (req, res) {
+  res.header('Access-Control-Allow-Origin', '*');
+  res.header('Access-Control-Allow-Methods', 'GET,POST,OPTIONS');
+  res.send(200);
+});
+*/
+
+app.use(cors());
+
 app.use('/graphql', graphqlHTTP({
   schema: schema,
   rootValue: root,
   graphiql: true,
 }));
-app.use(cors());
 
 app.listen(config.port || 4000);