Laravel 8 has a nice feature secret route for maintenance bypass. You can get this feature in Laravel 6 or laravel 6 with a simple package called haruncpi/laravel-maintenance.
// install
composer require haruncpi/laravel-maintenance
//Now replace default maintenance middleware
//\App\Http\Middleware\CheckForMaintenanceMode::class,
\Haruncpi\LaravelMaintenance\Middleware\MaintenanceMode::class,
//usages
php artisan down --secret="mysecretkey"
//maintenance bypass
https://example.com/mysecretkey
//GitHub repo: https://github.com/haruncpi/laravel-maintenance