Close the workbook

Author: Rajeev Kumar Singh

src/main/java/ExcelWriter.java

@@ -99,6 +99,8 @@ Hyperlink, RichTextString etc in a format (HSSF, XSSF) independent way */
         FileOutputStream fileOut = new FileOutputStream("poi-generated-file.xlsx");
         workbook.write(fileOut);
         fileOut.close();
+
+        workbook.close();
     }