data.go
func NewDataFile(f *os.File) (*Data, error) {
	d := newData()
	return d, handleError(C.gpgme_data_new_from_fd(&d.dh, C.int(f.Fd())))
}
func NewDataFile(f *os.File) (*Data, error) {
	d := newData()
	return d, handleError(C.gpgme_data_new_from_fd(&d.dh, C.int(f.Fd())))
}
// NewDataFile returns a new file based data buffer