Google calendar events can be synced through the Apple calendar and at least for me by default have reminders set 30 minutes before. I have my account set up through the mail app, but to check thus do the following:

Go to Settings -> Calendar -> Accounts -> Gmail. Make sure it’s set to sync your calendar. There’s also the ability to add an account here. Then go back to the calendar app and find an event to check if reminders are set.