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 ...
