code: func New(authenticator authenticator.Token, cacheErrs bool, successTTL, failureTTL time.Duration) authenticator.Token {
  	return newWithClock(authenticator, cacheErrs, successTTL, failureTTL, utilclock.RealClock{})
  }
docs: // New returns a token authenticator that caches the results of the specified authenticator. A ttl of 0 bypasses the cache.