code: func New(authTokenHandlers ...authenticator.Token) authenticator.Token {
  	if len(authTokenHandlers) == 1 {
  		return authTokenHandlers[0]
  	}
  	return &unionAuthTokenHandler{Handlers: authTokenHandlers, FailOnError: false}
  }
docs: // New returns a token authenticator that validates credentials using a chain of authenticator.Token objects.
  // The entire chain is tried until one succeeds. If all fail, an aggregate error is returned.