Modules not loading config files

Guess it does not work when the file is oudside of the app folder, but why would I add constants in the Common.php of the main app folder for a module that is loaded in in the Modules direcrory? Why is it so hard to add constants in a specific module? Guess I will need to use the crude solution.

directory structure
>app
>modules
->Admin (I want constants in here)
->Users
->...
>public
>vendor
>...