Display Related Posts in WordPress without a Plugin

<?php

$related = get_posts( array( 'category__in' => wp_get_post_categories($post->ID), 'numberposts' => 5, 'post__not_in' => array($post->ID) ) );
if( $related ) foreach( $related as $post ) {
setup_postdata($post); ?>
 <ul>
        <li>
        <a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a>
            <?php the_content('Read the rest of this entry &raquo;'); ?>
        </li>
    </ul>
<?php }

-------=--=-=-=-

<?php
                        $related = new WP_Query(
                          array(
                         'category__in'   => wp_get_post_categories( $post->ID ),
                         'posts_per_page' => 2,
                         'post__not_in'   => array( $post->ID )
                          )
                       );

                        $user = wp_get_current_user();
                        if( $related->have_posts() ) {
                        while ($related->have_posts()) : $related->the_post(); ?>
                         <div class="col-xl-6 col-md-6 col-12">
                            <div class="single-blog-item">
                                <div class="featured-thumb">
                                    <img src="<?php the_post_thumbnail(); ?>" alt="<?php the_title(); ?>">
                                </div>
                                <?php if( '1' == $is_post_date): ?>
                                <span class="post-date"><?php the_time(get_option('date_format')) ?></span>
                                <?php endif; ?>
                                <div class="post-meta">
                                    <div class="post-athuor">
                                        <?php if ($user) : ?>
                                        <div class="author-img" style="    background-image: url(<?php echo esc_url(get_avatar_url($user->ID)); ?>)"></div>
                                        <?php endif; ?>
                                        <a href="<?php echo get_author_posts_url(get_the_author_meta('ID'), get_the_author_meta('user_nicename')); ?>"><?php the_author(); ?></a>
                                    </div>
                                    <div class="post-comment">
                                        <a href="<?php the_permalink() ?>"><i class="far fa-comment-dots"></i><?php echo get_comments_number(); ?> Comments</a>
                                    </div>
                                </div>
                                <div class="post-content">
                                    <h3><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h3>
                                    <p><?php echo strip_shortcodes(saasnext_excerpt('saasnext_opt', 'blog_excerpt', true)); ?></p>
                                    <a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>" class="read-btn">Read More <i class="far fa-long-arrow-alt-right"></i></a>
                                </div>
                            </div>
                        </div>
                        <?php
                        endwhile;
                        wp_reset_postdata();
                        }
                    ?>