code: func (s *Client) GaugeDelta(stat string, value int64, rate float32) error {
  	if !s.includeStat(rate) {
  		return nil
  	}
  
  	// if negative, the submit formatter will prefix with a - already
  	// so only special case the positive value
  	if value >= 0 {
  		return s.submit(stat, "+", value, "|g", rate)
  	}
  	return s.submit(stat, "", value, "|g", rate)
  }
docs: // GaugeDelta submits a delta to a statsd gauge.
  // stat is the string name for the metric.
  // value is the (positive or negative) change.
  // rate is the sample rate (0.0 to 1.0).