How to protect your Laravel app with a secret key through 'artisan down'

"php artisan down" is a Laravel command that puts your application in maintenance mode. This means it is no longer available to your audience. But sometimes, you like to make it available for just a few people, like a secret project you are working on.

This is possible without any package or adding a password to your server.

[joldishopping]

How to add this real time project.. Can we explain that plz