To see if a user is already signed in

IfSignedIn.swift

AuthenticationManager.instance.getTokenSilently {
  (token: String?, error: Error?) in
  DispatchQueue.main.async {
      guard let _ = token, error == nil else {
          // If there is no token or if there's an error,
          // no user is signed in, so stay here
          return
      }
      // Since we got a token, a user is signed in
      // Go to welcome page
}