title: NodeJS - config cannot not load custom environment variables
body: <p>I am running <code>config@1.30.0</code> and I am attempting to get settings from the environment variables using <code>.\config\custom-environment-variables.json</code> does not work. However, it reads from the <code>.\config\default.json</code> just fine.</p>
  
  <p><code>.\config\custom-environment-variables.json</code></p>
  
  <pre><code>{
    "key": "app_key"
  }
  </code></pre>
  
  <p><code>.\config\default.json</code></p>
  
  <pre><code>{
    "key": "defaultKey"
  }
  </code></pre>
  
  <p>running</p>
  
  <pre><code>const config = require('config');
  console.log(config.get('key'))
  </code></pre>
  
  <p>always prints</p>
  
  <pre><code>defaultKey
  </code></pre>
  
  <p>but prints nothing when I set the <code>key</code> property in config/default to an empty string. How can I resolve this?</p>
  
  <h2>What I have tried</h2>
  
  <ol>
  <li>Opened a new console anytime I set the environment variable using set app_key=newKey</li>
  <li>Set the environment manually</li>
  </ol>