Refactor code structure for improved readability and maintainability

src/main.ts

@@ -3,7 +3,9 @@ import { AppModule } from "./app/app.module";
 
 async function bootstrap() {
   const app = await NestFactory.create(AppModule);
-  await app.listen(3000);
+
+  console.log(`Application is running on: ${process.env.PORT}`);
+  await app.listen(process.env.PORT);
 }
 
 bootstrap();