{% capture category_name %}{{ page.categories | first }}{% endcapture %}
{% for post in site.categories.[category_name] %}
{% if post.url == page.url %}
{% assign post_index0 = forloop.index0 %}
{% assign post_index1 = forloop.index %}
{% endif %}
{% endfor %}
{% for post in site.categories.[category_name] %}
{% if post_index0 == forloop.index %}{% assign next_post = post %}{% endif %}
{% if post_index1 == forloop.index0 %}{% assign prev_post = post %}{% endif %}
{% endfor %}
{% if prev_post %}{{ prev_post.title }}{% endif %}
{% if next_post %}{{ next_post.title }}{% endif %}