liwo/config/fcm.php

<?php

return [

    /*
    |--------------------------------------------------------------------------
    | FCM API Key
    |--------------------------------------------------------------------------
    |
    | This key allows you to send Push Notifications. To obtain this key go
    | to the porject settings and click on the "Cloud Messaging" tab, now
    | copy the API Key of "Legacy server key".
    |
    */

    'key' => env('FCM_KEY'),

];