class AppDelegate: NSObject, NSApplicationDelegate {

    @IBOutlet weak var window: NSWindow!
    var webView: WKWebView!

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        webView = WKWebView(frame: .zero, configuration: WKWebViewConfiguration())
        webView.navigationDelegate = self
    }
}

extension AppDelegate: WKNavigationDelegate {
    func webViewWebContentProcessDidTerminate(_ webView: WKWebView) {
        print("web view process did terminate")
        webView.reload()
    }
}