code: func (set *IntSet) ScanColumn(colIdx int, colName string, rd types.Reader, n int) error {
  	num, err := types.ScanInt64(rd, n)
  	if err != nil {
  		return err
  	}
  
  	setVal := *set
  	if setVal == nil {
  		*set = make(IntSet)
  		setVal = *set
  	}
  
  	setVal[num] = struct{}{}
  	return nil
  }
docs: // ScanColumn scans the columns and appends them to `IntSet`