[mabel] Modify middleware_example_2 to use arrow functions

Author: mabelleeyanhwa

middleware_example_2.js

@@ -24,12 +24,12 @@ const checkColor = () => {
 
 app.use(checkColor());
 
-app.get("/users", function(req, res) {
+app.get("/users", (req, res) => {
   console.log("users list was shown");
   res.send("Here is a list of users:....");
 });
 
-app.get("/books", function(req, res) {
+app.get("/books", (req, res) => {
   console.log("books list was shown");
   res.send("Here is a list of books:....");
 });