title: How to cancel Alamofire.upload
body: <p>I am uploading images on server via <code>Alamofire.upload</code> as multipart data. Unlike <code>Alamofire.request</code> it's not returning <code>Request</code> object, which I usually use to cancel requests. </p>
  
  <p>But it's very reasonable to be able to cancel such a consuming requests like uploading. What are the options for this in Alamofire?</p>