This worked for me!
- Synchronize Apple Calendar and Google Calendar by going to Settings -> Calendar -> Accounts -> Gmail(sign in to your account) -> turn on sync Calendars. As long as the notification is set up on Google Calendar, it will also notify you on Apple calendar.
- Then you can go to Settings -> Calendar Alerts. There you can set up a ringtone of your choosing that is long. Voila! Your notifications should now behave just like an alarm.
Note:
- Adding events to Apple Calendar will not add them to Google Calendar, but the other way around works! Add events to Google Calendar as usual.