To cache maps definitively roll back to version 3.1.28, which is the last version using google maps. No useful features have been added to the new Go versions. Just bloat. Unless you use Osmo -- whatever that is.
Here is, imho, why google maps are gone: Google changed the pricing for the google maps api usage. The change was announced last year and went into effect in July 2018. While to you, the end user, google maps is free, any developer using google maps as a component of an application, for instance DJI Go, has to pay. MapBox, open street maps = free.
Find a google maps version of the Go app here:
https://apkpure.com/dji-go-for-products-before-p4/dji.pilot
Download the .xapk not the .apk
Uninstall the Go version xx.xx.3x. The one you have that doesn't cache maps.
Install the xx.xx.28 which you just downloaded.
Because the Go app is complex there are some other steps to jump through for the install.
Change the .xapk to zip. unzip it on your android. move the newly unzipped directory structure: /android/obb/dji.pilot matching same directory on your device.
Install the unzipped .apk. you may have to enable allow install from unknown sources in the security settings of your device. GTS.
Complete instructions here.
How To Install XAPK Files Or Games On Android - MrGuider
Prepping to fly offline:
To cache the maps in the Go app connect your AC while online and zoom in to the area you intend to fly: all layers: map, sat, hybrid.
Maps are now cached.
Why are maps important?
For locating your aircraft if there is a mishap, in google maps download the area you are flying with the offline option. GTS.
Besides mapping where you are flying you can use the map In the Go app to find your aircraft if it is still running. Just look at the map and walk towards it. In the MC menu update your homepoint to the controller as you go. You can still do this with the blank Mapbox screen, but you have no visual reference from the satellite image -- "somewhere near that tall fir tree?!" If your AC is powered off mapbox is worthless in offline areas.
If you crash or your battery dies (while idling away in the distance) on the AC, you can't update the controller as homepoint as you walk towards the lost AC on the map. To find your lost AC, open google maps and eyeball the satellite image on Go and Google maps as you walk to where your non-active DJI Go, little-red-arrow is waiting for you.
Don't ask how I know this.
What Go needs as a feature is accesible last-known lat lng info of the AC. Plug that into google maps search and get the walking directions.
