code: func (s *StdoutClient) GaugeDelta(stat string, value int64) error {
  	// Gauge Deltas are always sent with a leading '+' or '-'. The '-' takes care of itself but the '+' must added by hand
  	if value < 0 {
  		return s.send(stat, "%d|g", value)
  	}
  	return s.send(stat, "+%d|g", value)
  }
docs: // GaugeDelta -- Send a change for a gauge