Wait Timeouts and Message Expirations for Channels

[marcoonroad]

To avoid blocking forever (while waiting for a message) and to provide a mechanism resembling a cache, timeouts and expirations are good abstractions over channels. The API will be the following, thus:

const message = await sporadicChannels.receive(channel, timeout)

Where timeout is optional, and:

const wasReceived = await sporadicChannels.send(channel, 'Hi, folks!', expiration)

Where expiration is optional too. The receive operation will fail/throw a Timeout error whenever a timeout occurs. For the case of send, it doesn't fails/throws (as is the case of receive), but wasReceived will be false whenever the expiration triggers and the message is erased (and thus, not received). Both timeout and expiration are units of time at ms (units compatible with JavaScript's setTimeout and setInterval).

Further discussions about implementation tradeoffs may be needed, but this API sketch is clean enough to not be changed later.

[marcoonroad]

To check directly if there's any message on channel, the client would just call:

let message = null
try {
  message = await sporadicChannels.receive(channel, 0)
} catch (reason) {
  // handles the case of empty channel here...
}

BUMP:
(It would be great to also cover that example on test suite.)

UPDATE:
Already covered, see:

sporadic/__tests__/channels-plus.js

Line 15 in 358f88f

const result1 = receive(channel, 0) // no block, check if there's a sent message

[marcoonroad]

BUMP:

Additional APIs provided:

const wasReceived = await channels.sendAfter(delayA, channel, msg, expiration)

...

const msg = await channels.receiveAfter(delayB, channel, timeout)

Both functions trigger their respective immediate counterparts scheduled on the future. Internally it's a setTimeout + wrapper Promise.