Argument 1 passed to Spatie\GoogleCalendar\GoogleCalendarFactory::createForCalendarId() must be of the type string, null given

google-calendar.php

<?php

return [

    /*
     * Path to the json file containing the credentials.
     */
    'service_account_credentials_json' => storage_path('app/google-calendar/service-account-credentials.json'),

    /*
     *  The id of the Google Calendar that will be used by default.
     */
    'calendar_id' => env('[email protected]'),
];

If i replaced 'calendar_id' => env('[email protected]'), to 'calendar_id' => '[email protected]', then it gives another error

file does not exist

Relative path of service-account-credentials.json is app\google-calendar\service-account-credentials.json

Relative path of google-calendar.php is config\google-calendar.php