Add custom featured image post navigation

Volume Custom Post Navigation

/* Volume Custom Post Navigation */
/* Markup in Hook Element: before_footer / execute PHP / Priority 100 */

<div id="post-nav">
	<?php global $post;
    $prevPost = get_previous_post(false);
        if($prevPost) {
            $args = array(
                'posts_per_page' => 1,
                'include' => $prevPost->ID
            );
            $prevPost = get_posts($args);
            foreach ($prevPost as $post) {
                setup_postdata($post);
    ?>
        <a class="post-previous" href="<?php the_permalink(); ?>">
				<div class="post-nav-wrap" style="background: linear-gradient(0deg,rgba(52,62,71,0.1),rgba(52,62,71,0.3)),url('<?php the_post_thumbnail_url(); ?>');">
            <div class="post-nav">Previous</div>
            <h3 class="post-nav-title"><?php the_title(); ?></h3>
        </div></a>
    <?php
                wp_reset_postdata();
            } //end foreach
        } // end if

        $nextPost = get_next_post(false);
        if($nextPost) {
            $args = array(
                'posts_per_page' => 1,
                'include' => $nextPost->ID
            );
            $nextPost = get_posts($args);
            foreach ($nextPost as $post) {
                setup_postdata($post);
    ?>
        <a class="post-next" href="<?php the_permalink(); ?>">
        <div class="post-nav-wrap" style="background: linear-gradient(0deg,rgba(52,62,71,0.6),rgba(52,62,71,0.3)),url('<?php the_post_thumbnail_url(); ?>');">
            <h3 class="post-nav-title"><?php the_title(); ?></h3>
            <div class="post-nav">Next</div>
        </div></a>
    <?php
                wp_reset_postdata();
            } //end foreach
        } // end if
    ?>
</div>

/* CSS CUSTOM POST NAVIGATION - ENSURE GP NAV IS DISABLED */

.post-nav {
    background-color: #ff3366;
    color: #fff !important;
}

#post-nav a {
    -webkit-box-flex: 1;
    -ms-flex: 1 0 50%;
    flex: 1 0 50%;
    box-sizing: border-box;
}

@media (max-width: 768px) {
    #post-nav a {
        -webkit-box-flex: 1;
        -ms-flex: 1 0 100%;
        flex: 1 0 100%;
    }
}

#post-nav .post-nav-wrap {
    background-size: cover !important;
    background-position: center center !important;
    min-height: 120px;
    height: 100%;
    padding: calc(6% + 1em) 5%;
    -webkit-box-shadow: inset 0 -50px 70px 20px rgba(0, 0, 0, 0.5);
    box-shadow: inset 0 -50px 70px 20px rgba(0, 0, 0, 0.5);
    -webkit-transition: -webkit-box-shadow 500ms;
    transition: -webkit-box-shadow 500ms;
    transition: box-shadow 500ms;
    transition: box-shadow 500ms, -webkit-box-shadow 500ms;
    position: relative;
}

#post-nav .post-nav-wrap:hover {
    -webkit-box-shadow: inset 0 -90px 70px 20px rgba(0, 0, 0, 0.5);
    box-shadow: inset 0 -90px 70px 20px rgba(0, 0, 0, 0.5);
}

.post-nav-wrap>* {
    color: #fff;
}

.post-nav-date {
    font-size: 0.9em;
}

.post-nav-title {
    margin: 5px 0 !important;
}

.post-nav {
    min-width: 60px;
    position: absolute;
    top: 0;
    border-radius: 0 0 2px 0;
}

.post-nav:first-child {
    left: 0;
}

.post-nav:last-child {
    right: 0;
}