Fix issue with retrieving the PORT environment variable

app.py

@@ -87,7 +87,7 @@ if __name__ == '__main__':
         db.create_all()
 
     # Retrieve the assigned port or default to 5000
-    port = int(os.environ.get('PORT', 5000))
+    port = int(os.getenv('PORT', 5000))
 
     # Run the app
     app.run(debug=True, port=port)