code: func readExpBackoffConfig() BackoffManager {
  	backoffBase := os.Getenv(envBackoffBase)
  	backoffDuration := os.Getenv(envBackoffDuration)
  
  	backoffBaseInt, errBase := strconv.ParseInt(backoffBase, 10, 64)
  	backoffDurationInt, errDuration := strconv.ParseInt(backoffDuration, 10, 64)
  	if errBase != nil || errDuration != nil {
  		return &NoBackoff{}
  	}
  	return &URLBackoff{
  		Backoff: flowcontrol.NewBackOff(
  			time.Duration(backoffBaseInt)*time.Second,
  			time.Duration(backoffDurationInt)*time.Second)}
  }
docs: // readExpBackoffConfig handles the internal logic of determining what the
  // backoff policy is.  By default if no information is available, NoBackoff.
  // TODO Generalize this see #17727 .