wp_async_js_load.php

function __clean_js($tag, $handle) {
    $__files = [
        'async' => [
            // 'recaptcha', // Plugin breaks
        ],
        'defer' => [
            'easy-testimonial',
            'contact-form-7',
            'themepunch',
        ],
    ];

    $replace = false;
    foreach ($__files as $mode => $files) {
        foreach ($files as &$file) {
            if(strpos($tag, $file) !== false){
                $replace = $mode;
                break;
            }
        }
    }

    if(! $replace){
        return $tag;
    }

    return str_replace( ' src', ' '.$replace.' src', $tag );
}
add_filter('script_loader_tag', '__clean_js', 10, 2);