google analytics

hi, i am having a problem form google analytics, i can not set up it. i have changed the code from includes/extensions/google-analytics.html and now is like this:

<script async src="https://www.googletagmanager.com/gtag/js?id={{ site.google_analytics }}"></script>
<script>
  function initGoogleAnalytics() {
    var doNotTrack = (window.doNotTrack === "1" || navigator.doNotTrack === "1" ||
      navigator.doNotTrack === "yes" || navigator.msDoNotTrack === "1");
    var enableDNT = "{{ site.enableDNT | default: true }}" == "true";

    if (!enableDNT || !doNotTrack) {
      window.dataLayer = window.dataLayer || [];
      function gtag(){window.dataLayer.push(arguments);}
      gtag('js', new Date());

      gtag('config', '{{ site.google_analytics }}');
        }
  }
  window.addEventListener("load", initGoogleAnalytics);
</script>
```

and my  `_config.yml`  

```
# Google analytics
google_analytics: [G-9DDM93FC22]
```

what is my error?