Synchronously:

if let filePath = Bundle.main.path(forResource: "imageName", ofType: "png"), let image = UIImage(contentsOfFile: filePath) {
    imageView.contentMode = .scaleAspectFit
    imageView.image = image
}

Asynchronously:

// Create a method with a completion handler to get the image data from the URL

func getData(from url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> ()) {
    URLSession.shared.dataTask(with: url, completionHandler: completion).resume()
}

// Create a method to download the image by starting the task

func downloadImage(from url: URL) {
    print("Download Started")
    getData(from: url) { data, response, error in
        guard let data = data, error == nil else { return }
        print(response?.suggestedFilename ?? url.lastPathComponent)
        print("Download Finished")
        DispatchQueue.main.async() {
            self.imageView.image = UIImage(data: data)
        }
    }
}

Usage:

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view
    print("Begin of code")
    if let url = URL(string: "https://examplepull-hexid.kxcdn.com/img/logo.png") {
        imageView.contentMode = .scaleAspectFit
        downloadImage(from: url)
    }
    print("End of code. The image will continue downloading in the background and it will be loaded when it ends.")
}

Extension:

extension UIImageView {
    func downloaded(from url: URL, contentMode mode: UIViewContentMode = .scaleAspectFit) {  // for Swift 4.2 syntax just use => mode: UIViewContentMode
        contentMode = mode
        URLSession.shared.dataTask(with: url) { data, response, error in
            guard
                let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200,
                let mimeType = response?.mimeType, mimeType.hasPrefix("image"),
                let data = data, error == nil,
                let image = UIImage(data: data)
                else { return }
            DispatchQueue.main.async() {
                self.image = image
            }
        }.resume()
    }
    func downloaded(from link: String, contentMode mode: UIViewContentMode = .scaleAspectFit) {  // for Swift 4.2 syntax just use => mode: UIViewContentMode
        guard let url = URL(string: link) else { return }
        downloaded(from: url, contentMode: mode)
    }
}

Usage:

imageView.downloaded(from: "https://examplepull-hexid.kxcdn.com/img/logo.png")