To add on, the go-github package works partially, in that github.ValidatePayload won’t work (invalid payload signature from Gitea), but if you pass the request body bytes in to github.ParseWebHook, it does marshal the payload into the corresponding type and you can properly type switch to handle it. The result, however, is you only get part of the GItea event payload.
If there’s not a similar Gitea webhook client package (like the very convenient and easy to use github version) I’d be happy to start working up a PR. Being my first contribution to the Gitea project, a hint as to where the client package should live would be helpful.