title: Elixir Phoenix not loading env variable at runtime
body: <p>I am trying to load an API key as a system env from my mac when starting up the phoenix server. What am I getting wrong? these are my steps:</p>
  
  <ol>
  <li><p>On my mac terminal:</p>
  
  <pre><code>export API_NOTIFICATION_KEY=1234
  </code></pre></li>
  <li><p>in my config.exs</p>
  
  <pre><code>config :app, App.Notifications,
  notification_api_key: {:system, "API_NOTIFICATION_KEY"}
  </code></pre></li>
  <li><p>in my module where I use it</p>
  
  <pre><code>@api_notification_key Application.get_env(:app, App.Notifications)[:notification_api_key]
  </code></pre></li>
  <li><p>start my phoenix server</p>
  
  <pre><code>mix phx.server
  </code></pre></li>
  </ol>
  
  <p>And then When I try to make the API call it is showing as nil. Is there a step I am missing to get it properly loaded ?</p>