wkwebview start loading delegate
var loadCount: Int = 0
override func viewDidLoad() {
    super.viewDidLoad()
    startLoading()
    webview.navigationDelegate = self
    let request = URLRequest(url: url)
    webview.load(request)
}
func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
    loadCount += 1
}
func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    loadCount -= 1
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) { [weak self] in
        if self?.loadCount == 0 {
            self?.stopLoading()
        }
    }
}
