value.go
func zeroValueOf(t reflect.Type) reflect.Value {
	zeroMutex.RLock()
	v, ok := zeroCache[t]
	zeroMutex.RUnlock()

	if !ok {
		v = reflect.Zero(t)
		zeroMutex.Lock()
		zeroCache[t] = v
		zeroMutex.Unlock()
	}

	return v
}
func zeroValueOf(t reflect.Type) reflect.Value {
	zeroMutex.RLock()
	v, ok := zeroCache[t]
	zeroMutex.RUnlock()

	if !ok {
		v = reflect.Zero(t)
		zeroMutex.Lock()
		zeroCache[t] = v
		zeroMutex.Unlock()
	}

	return v
}
// zeroValueOf and the related cache is used to keep the zero values so they
// don't need to be reallocated every time they're used.