category post qurey by shortcode

function category_post_shortcode($atts){
	extract( shortcode_atts( array(
		'title' => '',
		'link' => '',
		'category' => '',
	), $atts, 'category_post' ) );

    $q = new WP_Query(
        array( 'category' => $category, 'posts_per_page' => '3', 'post_type' => 'post')
        );
$list = '<div class="latest_from_category"><h2 class="latest_frm_cat_title">'.$title.'</h2> <a href="'.$link.'" class="latest_more_link">more</a>';

while($q->have_posts()) : $q->the_post();
    //get the ID of your post in the loop
    $id = get_the_ID();

    $post_excerpt = get_post_meta($id, 'post_excerpt', true);
	$post_thumbnail= get_the_post_thumbnail( $post->ID, 'post-thumbnail' );
    $list .= '

						<div class="single_cate_post floatleft">
							'.$post_thumbnail.'
							<h3>'.get_the_title().'</h3>
							<p>'.$post_excerpt.'</p>
							<a href="'.get_permalink().'" class="readmore">Read More</a>
						</div>
	';
endwhile;
$list.= '</div>';
wp_reset_query();
return $list;
}
add_shortcode('category_post', 'category_post_shortcode');