code: func AddInteger(a uint64, b int64) (uint64, error) {
  	if b >= 0 {
  		return AddUint64(a, uint64(b))
  	}
  
  	if uint64(-b) > a {
  		return 0, ErrOverflow.GenWithStackByArgs("BIGINT UNSIGNED", fmt.Sprintf("(%d, %d)", a, b))
  	}
  	return a - uint64(-b), nil
  }
docs: // AddInteger adds uint64 a and int64 b and returns uint64 if no overflow error.