code: func verifyLockTime(txLockTime, threshold, lockTime int64) error {
  	// The lockTimes in both the script and transaction must be of the same
  	// type.
  	if !((txLockTime < threshold && lockTime < threshold) ||
  		(txLockTime >= threshold && lockTime >= threshold)) {
  		str := fmt.Sprintf("mismatched locktime types -- tx locktime "+
  			"%d, stack locktime %d", txLockTime, lockTime)
  		return scriptError(ErrUnsatisfiedLockTime, str)
  	}
  
  	if lockTime > txLockTime {
  		str := fmt.Sprintf("locktime requirement not satisfied -- "+
  			"locktime is greater than the transaction locktime: "+
  			"%d > %d", lockTime, txLockTime)
  		return scriptError(ErrUnsatisfiedLockTime, str)
  	}
  
  	return nil
  }
docs: // verifyLockTime is a helper function used to validate locktimes.