Load WKWebView in Background Process

MyViewController.swift

           var start = NSDate()
            
            for i in 0...9
            {
                self.webViews.append(WKWebView())
            }
            
            let end = NSDate();
            NSLog("creating  webviews  \(end.timeIntervalSinceDate(start))")
            
            dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),{

                // Perform long running process
                var start = NSDate()
                for item in self.webViews
                {
                    var url : NSURL? = NSURL(string:"http://google.com")
                    var req = NSURLRequest(URL:url!)
                    item.loadRequest(req)
                }
                let end = NSDate();
                NSLog("done loading requests  \(end.timeIntervalSinceDate(start))")
            
            dispatch_async(dispatch_get_main_queue(),{
                
                
                var start = NSDate()

                self.scrollView!.contentSize = CGSizeMake(self.view.bounds.width, (self.view.bounds.height - 50.0) * CGFloat(11))
                
                var i = 0
                for item in self.webViews
                {
                    item.frame = CGRectMake(0, self.view.bounds.height * CGFloat(i),
                        self.view.bounds.width, self.view.bounds.height)
                    
                     self.scrollView!.addSubview(item)
                    i++
                }
                
                let end = NSDate();
                NSLog("done adding webviews to frame  \(end.timeIntervalSinceDate(start))")
               
                
                });
            });