code: func gogpgme_assuan_data_callback(handle unsafe.Pointer, data unsafe.Pointer, datalen C.size_t) C.gpgme_error_t {
  	c := callbackLookup(uintptr(handle)).(*AssuanDataCallback)
  	if *c == nil {
  		return 0
  	}
  	(*c)(C.GoBytes(data, C.int(datalen)))
  	return 0
  }
docs: //export gogpgme_assuan_data_callback