To use your Bitcoin Gold, you need to control the private key. From the last fork:
Announcement regarding BIP148/BIP91 SegWit soft fork upgrade and enforcement:
If you wish to be able to spend coins on a chain that clones the Bitcoin ledger, we advise that you move your coins from GreenAddress to a wallet that will allow you to split your coins safely. Coins that are held in GreenAddress may not be able to be split, and transactions that occur on GreenAddress may be replayed on the forked chain.
I never use any wallet that doesn't give me full access to my own private keys.