That's actually the same code I received. So it's multi use.
Dear Vault Hunter,
If you are reading this email, it means the Earth hasn't exploded! Celebrate with this SHiFT code for a Golden Key in Borderlands 2:
To redeem your code from Borderlands 2 Main Menu, select Extras then SHiFT Code and follow the on-screen instructions. For help and assistance with SHiFT, visit:
Be sure to use them before it's too late! You never know when the world may end...
Now get back in there and save Pandora!
-2K Games and Gearbox