No Application Encryption Key Has Been Specified : laravel

Before using Laravel encrypted, you must set a key option in your config/app.php configuration file.

You should generate key here are the following the steps.

STEP 1) Copy .env.example to .env:   (if you don't have .env file in root folder)

$ cp -a .env.example .env

STEP 2) Generate a new key : 

$ php artisan key:generate

Step 3) Run project

$ php artisan serve