you don't need to claim bitcoin gold by yourself i think , you just need to send your bitcoin to any trusted exchange that provide bitcoin gold
such as yobit ... and so on , i don;t know if there have anyother exchange support that , but yobit i know they provide bitcoin gold cliam,
You shouldn't really on any online wallet to provide those coins for you, better to own the privkey.
I wouldn't call yobit a trusted exchange either by the way.