How to check if a user has an active iOS auto-renewable subscription from server?

Question

My iOS app offers auto-renewable subscriptions. Only the users that has non-expired subscriptions are supposed to receive some news alerts through push notifications. Currently I thought of two possible ways to implement this. One is to subscribe and unsubscribe to push notification from the app by checking the subscription state during the application launch and send push notifications to all subscribers from the server-side.The second method is to update the expiration date of the subscription to the server and make the server checking if the subscription is expired before sending push notifications.

I understand that both methods will always require the app to be launched frequently to update the subscription status. Is there any other way to handle this task? Any tips/suggestions would be highly appreciated. Thanks!