title: Can't read new config variables in laravel 5.4
body: <p>I added a new config variable to the <code>config/app.php</code> file in laravel like this </p>
  
  <blockquote>
    <p><code>'foo'  =&gt; 'pass'</code></p>
  </blockquote>
  
  <p>but when I tried reading it using <code>config('app.foo')</code> I keep getting <code>null</code> while other variables return correct values. What do I need to do?</p>