There's many over the web. You can look at this to configure your VSCode https://dartcode.org/docs/using-dart-define-in-flutter/ and this to configure your app to use your dart defines vars in your ios and android native code https://medium.com/flutter-community/how-to-setup-dart-define-for-keys-and-secrets-on-android-and-ios-in-flutter-apps-4f28a10c4b6c