Since iOS 11 the location permission model is more strict. Developers are not allowed to support "Always" only anymore. Apple advices a 2 step approach to ask users for the "Always" support as explained in this blogpost:
The current geolocation module doesn't support this strategy though due to this check: https://github.com/appcelerator/titanium_mobile/blob/822b2eeca1af07d6405ec47e5a33568b12362939/iphone/Classes/GeolocationModule.m#L816
Because of this, you won't be able to support the advised approach to require users to authorise the 'Always' mode which is needed to support geofences and beacon technology.
Read more here.
Edit by Hans: In addition, there is another new constant called NSPhotoLibraryAddUsageDescription that is now required when attempting to write to the photo-gallery. It works without this change, but this change will warn the user if it's not set to track down the changes more easily.
P.S.: (by Hans): Apple made a typo in the above article. It is NSLocationAlwaysAndWhenInUseUsageDescription, not NSLocationAlwaysAndWhenInUsageDescription. I filed a radar for Apple regarding that.