Is there any way to do a

get

inside a

return HttpClient(OkHttp) {
  //For instance if I want to update a refreshToken
}

It's definitely possible if you implement your own feature. Copy the code from

OAuthFeature

and modify it pass the client to the lambdas.

But the thing is how do I do a

get

in the lambda? If to do so I need an HttpClient, right?

You'll have the

HttpClient

when installing the feature.

How do I get reference of HttpClient? For instance if I have a service that via parameter receives an httpclient how do I call this? Service(httpClient:HttpClient) inside the feature?

I misread your question at first, but you will probably be looking for features. Usually you cannot use an object while configuring it, exactly like here.