Shortcode with ‘year’ parameter

With help from @bosco , I was able to figure it out. Below is the working code:

//get archived posts per year
add_shortcode( 'archived-posts', 'archived_posts' );
function archived_posts($atts) {
    $a = shortcode_atts( array( 'year' => date('Y') ), $atts );

    $q = new WP_Query(array(
        'post_type' => 'post',
        'posts_per_page' => -1 ,
        'post_status' => 'archive' ,
        'year' => $a['year'],
    ));
    while ($q->have_posts()) {
        $q->the_post();
        $buffer .= '<div class="archived-post-item"><a href="'.get_permalink().'">'.get_the_title().'</a></div>';
    }
    wp_reset_postdata();
    return $buffer;
}