code: func sysCredWrite(cred *Credential, typ sysCRED_TYPE) error {
  	ncred := sysFromCredential(cred)
  	ncred.Type = uint32(typ)
  	ret, _, err := procCredWrite.Call(
  		uintptr(unsafe.Pointer(ncred)),
  		0,
  	)
  	if ret == 0 {
  		return err
  	}
  
  	return nil
  }
docs: // http://msdn.microsoft.com/en-us/library/windows/desktop/aa375187(v=vs.85).aspx