cronos

I believe you have a race in that code on error channel. You can't guarantee that the value you send on it will be received by correct receiver. If you have 2 concurrent transfers and one errors and the other succeds, second one may receive an error intended for the first one.

Why exactly do Resource's methods take variadic argument? In what scenario can there be more than one?

Also, small remarks about code: You define type HandleFunc in your package which is identical to http.HandlerFunc. Looks like it can be removed. Some error logging (rw.Write, json.Marshal) would be useful as well.