add_shortcode('custom_message', 'codebykp_display_custom_message');
function codebykp_display_custom_message($atts) {
    $atts = shortcode_atts(array(
        'text' => 'Hello, World!',
    ), $atts);

    return '<div class="custom-message">' . esc_html($atts['text']) . '</div>';
}