How can I send message to user but I only know userid?

[gdgrc]

send with username is ok as below

waitToSendPeer, _:= tc.Resolver.ResolveDomain(ctx, "xxx")

err = tc.RawClient.SendMessage(ctx, &tg.MessagesSendMessageRequest{
Peer:    waitToSendPeer,
Message: "good",
})

I get userId and accesshash when in OnNewChannelMessage. But I can not send with userid and accesshash getting PEER_ID_INVALID. I try to compare userid,accesshash with the one resolved by username and I find accesshash is diffrerent. why?