force download a file in template_redirect hook

The solution is in fact very simple. Just use the action admin_post_(action)…

add_action( 'admin_post_export_page', 'export_page' );
function export_page() {
    // any code you want
}

than you can make custom links admin_url( ‘admin-post.php?action=export_page&id=’ . $post->ID );

Thanks Milo for giving the solution.