WordPress Single Post Nav

wp-single-post-nav.php

<?php
if ( ! function_exists( 'mytheme_post_nav' ) ) :
  /**
   * Display navigation to next/previous post when applicable.
   *
   * @return void
   */
  function mytheme_post_nav() {
    // Don't print empty markup if there's nowhere to navigate.
    $previous = ( is_attachment() ) ? get_post( get_post()->post_parent ) : get_adjacent_post( false, '', true );
    $next     = get_adjacent_post( false, '', false );

    if ( ! $next && ! $previous ) {
      return;
    }
?>
  <nav class="navigation posts-navigation">
   <div class="post-nav-box">
    <h2 class="screen-reader-text"><?php esc_html_e( 'Post navigation', 'mytheme' ); ?></h2>
    <div class="nav-links">
<?php
    previous_post_link( '<div class="nav-previous"><span class="nav-indicator"><span class="screen-reader-text">' . __( 'previous:', 'mytheme' ) . '</span></span><h5>%link</h5></div>', '%title', TRUE, '' );
    next_post_link( '<div class="nav-next"><span class="nav-indicator"><span class="screen-reader-text">' . __( 'next:', 'mytheme' ) . '</span></span><h5>%link</h5></div>', '%title', TRUE, '' );
?>
    </div><!-- .nav-links -->
   </div><!-- .post-nav-box -->
  </nav><!-- .navigation -->
<?php
  }
endif; ?>

Above goes in an includes file like: inc/template-tags.php.
In template-parts/content-single.php at the bottom of the page: <?php refugees_post_nav(); ?>