How to authenticate Game Center (GameKit) on an Apple Watch

I need a way where you can view a leaderboard from an Apple Watch. I have seen Apple Watch Apps which do what I want to do. I know how to get the leaderboard and all that. But what I need help with is how do I authenticate Game Center on Apple Watch. Because Apples authentication Handler isn't compatible with watchOS. See here for more information on authenticateHandler.
I'm guessing I need to use background to fetch the authantication handler from the connected iPhone. But I don't have any experience in using background. So I wouldn't know how I go about doing that if that is the only solution?
Also, Using WatchConnectivity is another way. But again I don't know how to approach this. Any help would be nice!
Here is my authentication method for iOS:

Code Block 
func authenticateLocalPlayer() {
				LocalPlayer.authenticateHandler = { [self] viewController, error in
						if ((viewController) != nil) {
								self.present(viewController!, animated: true, completion: {
								})
						} 
						let isGameCenterReady = (viewController == nil) && (error == nil)
						if isGameCenterReady {
								if LocalPlayer.isAuthenticated {
										//is Authenticated
								} else {
										//not
								}
						} 
				}
		}

But the authenticateHandler isn't available for watchOS.
I tried just using the isAuthenticated But that returned false because authenticate handler wasn't called.


I am open to solving this question anyway!