code: func diskStats() (*disk, error) {
  	var (
  		freeBytes  uint64 = 0
  		totalBytes uint64 = 0
  	)
  
  	// windows sets return value to 0 when function fails.
  	ret, _, err := procGetDiskFreeSpaceExW.Call(
  		0,
  		uintptr(unsafe.Pointer(&freeBytes)),
  		uintptr(unsafe.Pointer(&totalBytes)),
  		0,
  	)
  	if ret == 0 {
  		return nil, err
  	}
  
  	// diskStats functions from other platforms return disk usage in kiB.
  	return &disk{
  		Usage: (totalBytes - freeBytes) / 1024,
  		Total: totalBytes / 1024,
  	}, nil
  }
docs: // diskStats returns information about the amount of space that is available on
  // a current disk volume for the user who calls this function.