code: func MinTTL(a, b time.Duration) time.Duration {
  	if a == 0 {
  		return b
  	}
  	if b == 0 {
  		return a
  	}
  	if a < b {
  		return a
  	}
  	return b
  }
docs: // MinTTL finds min non 0 TTL duration,
  // if both durations are 0, fails