AWS Cognito User Pool + Facebook Login iOS - ios

Question

I have started integrating AWS Cognito User Pools into my app and the signup + login works (I have followed this tutorial: https://docs.aws.amazon.com/cognito/latest/developerguide/tutorial-integrating-user-pools-ios.html)
Now I'm struggling to properly integrate a Facebook login. This is what I do:
After the user has successfully signed in with facebook (using the facebook SDK), I'm getting the token and calling this function:
func signInFacebook(){
let customProviderManager = CustomIdentityProvider(tokens: nil)
self.credentialsProvider = AWSCognitoCredentialsProvider(
regionType:CognitoIdentityUserPoolRegion,
identityPoolId: CognitoIdentityPoolId,
identityProviderManager: customProviderManager)
let configuration = AWSServiceConfiguration(region:CognitoIdentityUserPoolRegion, credentialsProvider: self.credentialsProvider!)
AWSServiceManager.default().defaultServiceConfiguration = configuration
}
My CustomIdentityProvider class looks like this:
class CustomIdentityProvider: NSObject, AWSIdentityProviderManager {
var tokens : NSDictionary?
init(tokens: NSDictionary?) {
self.tokens = tokens
}
func logins() -> AWSTask<NSDictionary> {
if let fbToken = AccessToken.current?.authenticationToken {
return AWSTask(result: [AWSIdentityProviderFacebook: fbToken])
} else if let googleToken = GIDSignIn.sharedInstance().currentUser.authentication.idToken {
return AWSTask(result: [AWSIdentityProviderGoogle: googleToken])
}
return AWSTask(error:NSError(domain: "Social login", code: -1 , userInfo: ["Social login" : "No current social access token"]))
}
}
After signInFacebook() is called, I also call
self.credentialsProvider?.credentials().continueOnSuccessWith { (task:AWSTask<AWSCredentials>) -> Any? in
print("credentials: \(task.result!)")
return nil
}
and it prints some data in the log which looks fine.
But for some reason it doesn't seem to link properly everything together.
When I'm calling my backend to fetch some data, I usually do it like this:
I call self.user?.getSession().continueOnSuccessWith (user is an instance of AWSCognitoIdentityUser) and inside the closure I build the request where I put the token in the header. But if there are no tokens, the SDK shows my login screen. And this is what happens all the time. I would expect the user object to be updated with the correct tokens after the social login with Facebook has succeeded. What am I doing wrong?