why laravel 5.6 returns file does not exist error?

I putted file on project-dir/client_secret_1***.apps.googleusercontent.com.json and then added variable into env file.

GOOGLE_PLAY_CREDENTIAL=http://local.project-dir/client_secret_1***.apps.googleusercontent.com.json

and then in config/services.php

return [

    'google_play' => [
        'credential' => env('GOOGLE_PLAY_CREDENTIAL'),
    ],

];

So now when I use it as like below

$client->setAuthConfig(config('services.google_play.credential'));

it is returning error which is

"file "http://local.project-dir/client_secret_1***.apps.googleusercontent.com.json" does not exist"

Can someone kindly guide me, where I am wrong so that I can fix the issue. I would like to appreciate.

Thanks

via Chebli Mohamed