Add option to invoke via async route

[alexellis]

As a user I would like to consume events from a queue and then have them processed by my existing asynchronous queue workers over NATS Streaming so that I can have one single way to process all events and asynchronous code.

[daikeren]

@alexellis What's your preferred way of supporting async function? One possible solution might be add another annotation to function (maybe something like async: true ?)

Is there any suggestion?

[alexellis]

cc @martindekov @tessellator

@daikeren I think async_invoke as an env-var would work.

[martindekov]

Derek assign: me

[martindekov]

I will try to implement this as soon as I can this time this week and will ping 👍

[alexellis]

Can you check the PR #27 please?

[martindekov]

Should I augment this PR to be optional the asynchronous or adding call to the asynchronous gateway path to the connector SDK?

[martindekov]

I was thinking of two approaches, amend the asynchronous path to where we configure the gateway URL so now its http://your.ip:port it would become http://your.ip:port/async-function/http://your.ip:port/function/ this would be the easiest approach, the second approach would be to add some sort boolean to the ControllerConfig(I need to make sure thats the most appropriate place). The former would just re-vendor the SDK with this simple change %s/function/%s -> %s/%s and add logic to the implementations of the connector which will build the gateway URL with async/non-async path appended.