WordPress filter that will add "async" to an enqueued script

add_async_to_script.php

#Assuming the script has already been enqueued with 'my-script' as a handle, add this to functions.php or to a plugin
add_filter( 'script_loader_tag', 'add_async_to_my_script', 10, 3 );
function add_async_to_my_script( $tag, $handle, $src ) {
  if ( $handle === 'my_script') {
$tag = '<script type="text/javascript" scr="' . esc_url($src) . '" async></script>';
  }
  return $tag;
}