Change port by env

src/app.ts

@@ -1,6 +1,8 @@
 import express from 'express';
 import { getLocationOfTarget } from './app.service';
 
+const port = Number(process.env.PORT) || 3000;
+
 const app = express();
 
 app.get('/*', async (req, res) => {
@@ -15,6 +17,6 @@ app.get('/*', async (req, res) => {
     }
 });
 
-app.listen(3000, () => {
-    console.log('Now listening on port 3000!');
+app.listen(port, () => {
+    console.log(`Now listening on port ${port}!`);
 });