code: func NewFailOnError(authRequestHandlers ...authenticator.Request) authenticator.Request {
  	if len(authRequestHandlers) == 1 {
  		return authRequestHandlers[0]
  	}
  	return &unionAuthRequestHandler{Handlers: authRequestHandlers, FailOnError: true}
  }
docs: // NewFailOnError returns a request authenticator that validates credentials using a chain of authenticator.Request objects.
  // The first error short-circuits the chain.