AppDelegate

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        let request = URLRequest(url: URL(string: "http://xxx.appspot.com/")!)
        NSURLConnection.sendAsynchronousRequest(request, queue: .main) { response, data, error in
            if let error = error {
                print(error)
            } else {
                print(response)
            }
        }

        return true
    }

NSExceptionDomains

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>NSAppTransportSecurity</key>
	<dict>
		<key>NSExceptionDomains</key>
		<dict>
			<key>xxx.appspot.com</key>
			<dict>
				<key>NSExceptionAllowsInsecureHTTPLoads</key>
				<true/>
			</dict>
		</dict>
	</dict>
    <!-- 中略 -->
</dict>
</plist>