title: Run a background thread on Swift 3
body: <p>I have a function that goes like this:</p>
  
  <pre><code>fileprivate func setupImageViewWithURL(url: URL) {
      var image: UIImage? = nil
      do {
          try image = UIImage(data: Data(contentsOf: url))!
      } catch is NSError {
          print("Failed")
      }
  
      image = self.imageWithImage(sourceImage: image!, scaledToWidth: UIScreen.main.bounds.size.width)
      self.imageImageView.image = image
      self.imageImageView.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: (image?.size.height)!)
  }
  </code></pre>
  
  <p>I want to run it on a <code>Background</code> <code>thread</code>.</p>
  
  <p>I've tried the <code>GDC</code> methods of <code>Swift2</code>, but it didn't work.</p>
  
  <p>Did anything change in the thread topic in <code>Swift3</code>?</p>
  
  <p>Thank you!</p>