single.php

<?php
/**
 * The template for displaying all single posts
 *
 * @link https://developer.wordpress.org/themes/basics/template-hierarchy/#single-post
 *
 * @package WP_Bootstrap_Starter
 */

get_header(); 
$image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' ); 
$post_time =  get_the_date('l, F j, Y')

?>


<div class="col-sm-12">
	<div style="width:100%;height:300px;background-image:url('<?= $image[0] ?>');background-size:cover;"></div>
	<div style="margin-top:1%;">
		<?php the_excerpt(__('Continue reading »','example')); ?>
	</div>
</div>

	<section id="primary" class="content-area col-sm-12 col-lg-12">
		<main id="main" class="site-main" role="main">

		<?php
		while ( have_posts() ) : the_post();

			get_template_part( 'template-parts/content', get_post_format() );

			    the_post_navigation();

			// If comments are open or we have at least one comment, load up the comment template.
			// if ( comments_open() || get_comments_number() ) :
			// 	comments_template();
			// endif;

		endwhile; // End of the loop.
		?>

		</main><!-- #main -->
	</section><!-- #primary -->

<?php
get_footer();