How can I get parameters in twig? I wrote a PHP script to deploy data to live-cdn and included a "deploy" button on the dashboard. the script returns ?success=true, and i need to show div element with "Congratulations"

i tried this with no success:

{% if app.request.query.get('success') %}
  &lt;div&gt;
    Glückwunsch! Deployment läuft.
  &lt;/div&gt;
{% endif %}
Actually, reading from the Craft 2 docs it's:

craft.request.getQueryString()      // returns the whole query string
craft.request.getQuery('success')   // returns only the value of 'success'