<script async src="https://www.googletagmanager.com/gtag/js?id=<%= ga_tracking_id %>"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  window.transport_url = "<%= transport_url %>";
  window.ga_tracking_id = "<%= ga_tracking_id %>";
  gtag('js', new Date());
  <% if current_user %>
    gtag('config', '<%= ga_tracking_id %>', {transport_url: '<%= transport_url %>', user_id: '<%= current_user.id %>'});
    gtag('config', '<%= ga_tracking_id %>', {user_id: '<%= current_user.id %>'});
  <% else %>
    gtag('config', '<%= ga_tracking_id %>', {transport_url: '<%= transport_url %>'});
    gtag('config', '<%= ga_tracking_id %>');
  <% end %>
</script>