file is not closed in some cases about pcidevices HOT 3 CLOSED

func unbindDeviceFromDriver(addr string, driver string) error {
	path := fmt.Sprintf("/sys/bus/pci/drivers/%s/unbind", driver)
	file, err := os.OpenFile(path, os.O_WRONLY, 0400)
..
	_, err = file.WriteString(addr)
	if err != nil {
                // file should be closed 
		return err   ////
	}
..
}

func unbindDeviceFromDriver(addr string, driver string) error {
...
	file, err := os.OpenFile(path, os.O_WRONLY, 0400)
..
       // after successfully OpenFile
       defer file.Close()   /// it will make sure, in any return path, file is closed

	_, err = file.WriteString(addr)

        // do NOT need any file.Close
...
..
}