code: func (m *CirconusMetrics) SetHistogramValue(metric string, val float64) {
  	hist := m.NewHistogram(metric)
  
  	m.hm.Lock()
  	hist.rw.Lock()
  	hist.hist.RecordValue(val)
  	hist.rw.Unlock()
  	m.hm.Unlock()
  }
docs: // SetHistogramValue adds a value to a histogram