You could do the following:

0. Make sure all your bitcoins and bitcoin cash is GONE from that address (a security best practice)

1. download the official BTG Core wallet from https://bitcoingold.org/downloads/ (make sure all keys of your download match).

2. Run it and synchronize it with the network (it may take from a couple of days to a couple of weeks)

3. Import your private key as you would do in bitcoin core (importprivkey command from the console)

4. You can now send it to your destination address and deinstall the core. Save the wallet.dat for security reasons (Satoshi recommended NEVER to delete your wallets)

That method has cons and pros. Pros - it is farely safe and secure as you don't compromise your private keys to any other party. Cons - it takes long to synchronize.