injector module error in angular

I have a problem with using a module in my angular app:

I installed async with bower install async

I added the script to index.html :

<script type="text/javascript" src="js/lib/ext/async/lib/async.js"></script>

I added "async": "0.9.0" to bower.json

Then, i injected the module in my app :

var app = angular.module('app', ['async',...])

And i get the following error :

Uncaught Error: [$injector:modulerr] Failed to instantiate module app due to: Error: [$injector:modulerr] Failed to instantiate module async due to: Error: [$injector:nomod] Module 'async' is not available! You either misspelled the module nam......1)

I found out i didn't have to inject async to my app nor to give it to my controller .. since it was not built for angular. What is needed is to add the script tag to index.html

<script type="text/javascript" src="js/lib/ext/async/lib/async.js"></script>

and that's all