WordPress: Adicionando link no post_thumbnail

//Adicionando e apontando o link do post_thumbnail para o seu respectivo post

add_filter( 'post_thumbnail_html', 'cms_post_image_html', 10, 3 );

function cms_post_image_html( $html, $post_id, $post_image_id ) {

    $html = '<a href="' . get_permalink( $post_id ) . '" title="' . esc_attr( get_post_field( 'post_title', $post_id ) ) . '">' . $html . '</a>';


  return $html;
}