code: func (c *StatsdClient) TimingWithSampling(stat string, delta int64, sampleRate float32) error {
  	if err := checkSampleRate(sampleRate); err != nil {
  		return err
  	}
  
  	if !shouldFire(sampleRate) {
  		return nil // ignore this call
  	}
  
  	return c.send(stat, "%d|ms", delta, sampleRate)
  }
docs: // TimingWithSampling - Track a duration event