something not very well under multi threads

[starxchina]

func (m *Measurement) getHist(op string, err error, current bool) *Histogram {
	opMeasurement := m.OpSumMeasurement
	if current {
		opMeasurement = m.OpCurMeasurement
	}

	// Create hist of {op} and {op}_ERR at the same time, or else the TPM would be incorrect
	opPairedKey := fmt.Sprintf("%s_ERR", op)
	if err != nil {
		op, opPairedKey = opPairedKey, op
	}

	m.RLock()
	opM, ok := opMeasurement[op]
	m.RUnlock()
	if !ok {
		opM = NewHistogram(m.MinLatency, m.MaxLatency, m.SigFigs)
		opPairedM := NewHistogram(m.MinLatency, m.MaxLatency, m.SigFigs)
		m.Lock()
		opMeasurement[op] = opM
		opMeasurement[opPairedKey] = opPairedM
		m.Unlock()
	}
	return opM
}

there will exist data loss under multi threads in pkg/measurement/measure.go: if !ok {...}