In Go HTTP handlers, why is the ResponseWriter a value but the Request a pointer?

Question

I'm learning Go by writing an app for GAE, and this is signature of a handler function:

func handle(w http.ResponseWriter, r *http.Request) {}

I'm pointer newbie here, so why is the Request object a pointer, but the ResponseWriter not? Is there any need to have it this way or is this just to make some kind of advanced pointer based code possible?

Answer 1

What you get for w is a pointer to the non exported type http.response but as ResponseWriter is an interface, that's not visible.

From server.go:

type ResponseWriter interface {
    ...
}

On the other hand, r is a pointer to a concrete struct, hence the need to pass a reference explicitly.

From request.go:

type Request struct {
    ...
}