urlsessiondemo1.swift

    @IBAction func action_loadImage(_ sender: UIButton) {
        //disable button in case user click twice
        sender.isEnabled = false
        //start loading image
        startLoad()
    }
    
    func startLoad() {
        let url = URL(string: "https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png")!
        
        let task = URLSession.shared.dataTask(with: url) { data, response, error in
            //if has error then return
            if let error = error {
                self.handleClientError(error)
            }
            
            //if status code not in 200~299 , then something happen on server side
            guard let httpResponse = response as? HTTPURLResponse, (200...299).contains(httpResponse.statusCode) else {
                self.handleServerError(response)
                return
            }
            
            //load image data
            if let mimeType = httpResponse.mimeType, mimeType == "image/png", let data = data{
                DispatchQueue.main.async {
                    self.imageview1.image = UIImage(data: data)
                    
                    self.button1.isEnabled = true
                }
            }
            
        }
        
        task.resume()
        
    }
    
    //handle client side error here
    func handleClientError(_ error: Error) {
        print("client side error")
    }
    
    //handle server side error here
    func handleServerError(_ response: URLResponse?) {
        print("server side error")
    }