If it is on your computer you should be able to do this i think. I don't think you have to be online to see your keys, anyway, just follow the steps and see if your keys appear.

1. Extract your private keys for your pre-fork BTG coins by following the appropriate steps in the list of providers below.

- Electrum
1) Open the menu "View" and click on "Show Addresses"
2) Then open the new tab "Addresses"
3) Right-click on the addresses that had Bitcoin before the fork, then click "Private key".
4) Click on the qrcode icon to show it.

Now that you got your private key(s) for the address(es) that contained BTC prior to the fork of August 1st:

2. Create a BCG wallet in coinomi.

3. Click on .../Sweep Wallet and paste or scan the BTC private key that you obtained in step 1.

Your forked coins should now appear in your Coinomi BCG wallet