Sorry, I didn't recheck the posted code above, there were typos because I
didn't copied directly from the problem I wanted to solved. It's fixed now.
I think I misunderstood the `cb` in `callback` argument. I thought it didn't
return any value since the manual didn't state it but before I put the return
type, the compiler complained "type mismatch" when I used the `{.async.}`
pragma, it expected `cb: proc(...): T` while I provided `cb: proc(...)`.
I solved it with synchronous `httpclient.get` before but now I think I can try
using asynchronous again.
Thanks for help
EDIT: nimsuggest didn't report an error when trying using `{.async}` but
compiler throw error about expecting type `Future`. Hmm.
