Implement SendCloser on gochan.Protocol

[dan-j]

I'm using the gochan protocol for some internal processing of events. I've built a series of cloudevents.Client like so:

1. Client #1 listens on HTTP for events
2. For each event received on #1 we send to client #2 using a gochan.Protocol sender.
3. Client #3 is receiving from the same gochan.Protocol used in #2
4. For each event received on #3 we send to another client #4 which uses HTTP to an external target.

There's currently no way to wait until all events have finished with the current implementation of gochan.Protocol since it doesn't implement protocol.SendCloser.

You can cancel the ctx passed to client.StartReceiver(), but if you have any outstanding messages not yet received the receiver returns io.EOF as expected.

Closing the underlying channel allows StartReceiver() to continue processing all messages until eventually it returns io.EOF due to the channel being closed, and not because ctx was cancelled.

All this involves is changing gochan.Protocol to have an additional method:

func (sr *SendReceiver) Close(ctx context.Context) error {
	return sr.sender.Close(ctx)
}

Is this sensible, or am I missing something?

[n3wscott]

Sounds good to me, want to make a PR and ping me?

Glad you are getting use out of that implementation!! Let's make it work as you need it!!

[dan-j]

Yeah, I'm using it to expand a single received event into multiple events and getting the benefit of it all being asynchronous; it's quite handy!