Shortcode featured image

/**/

<img src="assets/images/works/p1.jpg" alt="">
'.get_the_post_thumbnail($idd, 'slider-larger').'
/**/

function aboutme_shortcode($atts, $content = null) {
        extract(shortcode_atts(array(

        ), $atts));

                $q = new WP_Query(
                     array('posts_per_page' => '3', 'post_type' => 'profsingle')
                );
                        $list .= '

                        ';
                                while($q->have_posts()) : $q->the_post();
                                $image_id = get_post_thumbnail_id();
                                $image_url = wp_get_attachment_image_src($image_id,'medium');
                                $image_url = $image_url[0];
                                    $list .= '
                                                <div class="col-md-4 aboutMe aboutStory wow fadeInUp" style="">
                                                <h1 class="abtmetitle">'.get_the_title().'</h1>
                                    ';

                                    if($image_url) :
                                    $list .= '<img class="profileAv" alt="" src="'.$image_url.'"> ';
                                    endif;

                                    $list .= '
                                                    <p>'.get_the_content().'</p>
                                                </div>

                                            ';

                                endwhile;
                        $list .= '

                        ';
                wp_reset_query();

        return $list;
}
add_shortcode('aboutme', 'aboutme_shortcode');