upload_url = vk_client.docs.getMessagesUploadServer(type="audio_message", peer_id=vk_message.peer_id)
post_info = post(upload_url["upload_url"], files={"file": open("gtts.ogg", "rb")}).json()
audio_doc = vk_client.docs.save(file=post_info["file"])

audio_message = "doc{}_{}".format(
    audio_doc["audio_message"]["owner_id"], audio_doc["audio_message"]["id"]
)
if audio_message:
    vk_message.send(message_text=f"", attachment=audio_message)