Convert url to UIImage Swift3

I try to convert url to UIImage by using following code :

            let url = URL(string: "http://www.apple.com/euro/ios/ios8/a/generic/images/og.png")
            let sessionTask = URLSession.shared
            let request = URLRequest(url: url!)
            let task = sessionTask.dataTask(with: request, completionHandler: {(data: Data?, response: URLResponse?, error: Error?) -> Void in
                if (error == nil) {
                    let image: UIImage = UIImage(data: data!)!

                }

            })
            task.resume()

but it's not work for me, if-loop is not complied.