Not tried location services on Go yet but in managing some iPhone/Android App experiments a year or so back we had lot of issues in getting exact current location (across all platforms). At that point it would often return the location of 1hr ago (sometimes even a day ago).
It was hit & miss in testing to try and force a device location update with API calls (suspect FMGO is using same iPhone location APIs as we did with the native app).
It was suggested by some test users that if you manually went into Map Apps & got current location (both iOS and Android) that it would often force update the device location. Although not something we wanted to require users to do.
Never really go to the bottom of it. Was experimental project with ltd budget that got killed to focus on other ideas. I suspected the map apps probably use further browser based location service as a back up to native device APIs.
The above was with iOS4 & iPhone3/4 so would imagine iOS/device location has got better each update but its a problem with the iOS API & device updating its location rather than FMGo.
There are techniques to get location via the webviewer. http://www.supportgroup.com/explore/geolocation-with-filemaker-go/ which might be worth a backup check even if just in testing against the FMGo 12 functions.