OK, I used just normal function and it’s ok.
function twentytwentychild_widgets_init() {
register_sidebar( array(
'name' => __( 'Widget name', 'twentytwentychild' ),
'id' => 'after-post',
'description' => __( 'Widget desc.', 'twentytwentychild' ),
'before_widget' => '',
'after_widget' => '',
'before_title' => '',
'after_title' => '',
) );
}
add_action( 'widgets_init', 'twentytwentychild_widgets_init' );