This closes #1903, made GetCellStyle function concurrency safe

- Update comment of the function and unit test

cell_test.go

@@ -42,6 +42,9 @@ func TestConcurrency(t *testing.T) {
  assert.NoError(t, err)
  // Concurrency set cell style
  assert.NoError(t, f.SetCellStyle("Sheet1", "A3", "A3", style))
+ // Concurrency get cell style
+ _, err = f.GetCellStyle("Sheet1", "A3")
+ assert.NoError(t, err)
  // Concurrency add picture
  assert.NoError(t, f.AddPicture("Sheet1", "F21", filepath.Join("test", "images", "excel.jpg"),
  &GraphicOptions{

styles.go

@@ -2186,19 +2186,22 @@ func setCellXfs(style *xlsxStyleSheet, fontID, numFmtID, fillID, borderID int, a
 }
 
 // GetCellStyle provides a function to get cell style index by given worksheet
-// name and cell reference.
+// name and cell reference. This function is concurrency safe.
 func (f *File) GetCellStyle(sheet, cell string) (int, error) {
+ f.mu.Lock()
  ws, err := f.workSheetReader(sheet)
  if err != nil {
+ f.mu.Unlock()
  return 0, err
  }
+ f.mu.Unlock()
+ ws.mu.Lock()
+ defer ws.mu.Unlock()
  col, row, err := CellNameToCoordinates(cell)
  if err != nil {
  return 0, err
  }
  ws.prepareSheetXML(col, row)
- ws.mu.Lock()
- defer ws.mu.Unlock()
  return ws.prepareCellStyle(col, row, ws.SheetData.Row[row-1].C[col-1].S), err
 }