Silent Remote Notifications

AppDelegate.swift

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        if !application.isRegisteredForRemoteNotifications {
            application.registerForRemoteNotifications()
        }
        return true
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        print(deviceToken.reduce("", {$0 + String(format: "%02X", $1)}))
    }

    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
        completionHandler(.noData)
    }

Info.plist

<key>UIBackgroundModes</key>
<array>
	<string>remote-notification</string>
</array>

Notifications.entitlements

<key>aps-environment</key>
<string>development</string>

payload.json

{
    "aps" : {
        "content-available" : 1
    },
    "foo" : "bar",
    "acme" : 42
}