Get related posts based on current page's slug

_related_posts.html

<ul>
  {% for related_post in site.pages['works'].taxonomy['tags'][slug].posts %}
  <li>
    <h3>{{related_post.title}}</h3>
    <img src="{{related_post.assets.first.url}}">
    <a href="{{related_post.url}}">{{related_post.title}}</a>
    {{related_post.excerpt}}
  </li>
  {% endfor %}
</ul>