Migrating our API to Express

There are two ways to install Express: directly in the code itself or through the express-generator application generator tool. The express-generator tool installs the express CLI, which we can use to generate an application skeleton from. However, we won't be using that because it's mainly meant for client-facing applications, while we are just trying to build a server-side API at the moment. Instead, we'll add the express package directly into our code.

First, add the package into our project:

$ yarn add express

Now open up your src/index.js file, and replace our import of the http module with the express package. Also replace the current http.createServer and server.listen calls with express and app.listen. What was previously this:

...
import http from 'http';
...
const server = http.createServer(requestHandler);
server.listen(8080);

Would now be this:

...
import express from 'express';
...
const app = express();
app.listen(process.env.SERVER_PORT);

To help us know...