code: func (s *Sheet) SetColWidth(startcol, endcol int, width float64) error {
  	if startcol > endcol {
  		return fmt.Errorf("Could not set width for range %d-%d: startcol must be less than endcol.", startcol, endcol)
  	}
  	end := endcol + 1
  	s.maybeAddCol(end)
  	for ; startcol < end; startcol++ {
  		s.Cols[startcol].Width = width
  	}
  
  	return nil
  }
docs: //Set the width of a single column or multiple columns.