How to change dynamically APP_KEY in config/app.php in laravel

basically i want to give different different APP_KEY to different different user so, when i try to do this they give fatal error

    /*
    |--------------------------------------------------------------------------
    | Encryption Key
    |--------------------------------------------------------------------------
    |
    | This key is used by the Illuminate encrypter service and should be set
    | to a random, 32 character string, otherwise these encrypted strings
    | will not be safe. Please do this before deploying an application!
    |
    */

    'key' => Auth::User()->APP_KEY

    'cipher' => 'AES-256-CBC',

via Chebli Mohamed