This is what I would like to know because I am absolutely sure that I have some Bitcoin Gold from my bitcoin-Core private key, but so far I'm not seeing them.
Steps I took:
Downloaded Bitcoin-Gold-Core wallet. Moved the wallet.dat from my Bitcoin-Core wallet to my Bitcoin-Gold-Core Wallet directory. Synced the blockchain. Blockchain is now synced. I see a list of transactions of Bitcoin-Gold coming in and out but I don't see any balance.
EDIT: I need to also try the steps here:
https://coinomi.freshdesk.com/support/solutions/articles/29000013719-how-to-get-bitcoin-cash-from-many-wallet-software-services-with-coinomiApparently you can export your private key and import it into Coinomi and get your BTC gold. (ignore that it's for BCash, it works for BGold too).