code: func (d *txDependency) signalValidationResult(ns string, err error) {
  	d.mutex.Lock()
  	defer d.mutex.Unlock()
  
  	d.validationResultMap[ns] = err
  	d.cond.Broadcast()
  }
docs: // signalValidationResult signals that validation of namespace `ns`
  // for transaction `d.txnum` completed with error `err`. Results
  // are cached into a map. We also broadcast a conditional variable
  // to wake up possible callers of waitForAndRetrieveValidationResult