code: func MulUint64(a uint64, b uint64) (uint64, error) {
  	if b > 0 && a > math.MaxUint64/b {
  		return 0, ErrOverflow.GenWithStackByArgs("BIGINT UNSIGNED", fmt.Sprintf("(%d, %d)", a, b))
  	}
  	return a * b, nil
  }
docs: // MulUint64 multiplies uint64 a and b and returns uint64 if no overflow error.