title: Laravel 5.6 env('APP_BASE_URL') returns null
body: <p>In staging and production environment, when I try to get my custom defined variable from .env file, it returns null. I have tried creating new Key for APP and cleared all sort of caches, but result is same.</p>
  
  <pre><code>APP_NAME="App - Staging"
  APP_ENV=staging
  APP_KEY=&lt;HIDDEN_KEY&gt;
  APP_DEBUG=true
  APP_LOG_LEVEL=none
  APP_URL=https://staging.app.com
  
  APP_BASE_URL="https://app-staging.app.com"
  </code></pre>
  
  <p>Clearing Cache</p>
  
  <pre><code>php artisan config:clear                     
  php artisan cache:clear
  php artisan route:clear
  php artisan view:clear
  php artisan config:cache
  </code></pre>
  
  <p>But when using following in blade view gets nothing</p>
  
  <pre><code>env('APP_BASE_URL') returns null
  </code></pre>