Feat: add a timeout option to Peer

[huan]

Currently, we can only call failPendingRequests() to make all the pending requests fail.

Sometimes it's better to set a timeout value and let the request failed automatically when it runs time out.

The simplest modification should be to add a timeout argument to failPendingRequests(timeout: number), which can be called period and clean the timeout-ed requests.

A better way to implement it might integrate the timeout with the Peer class.
For example:

interface PeerOptions {
  timeout: number
}

class Peer {
  constructor(public options: PeerOptions) {
  }

  // request will be rejected if it did not get any response from the server after timeout milliseconds.
}

[julien-f]

Not sure I see the point of this, it's very easy to implement directly in onMessage or with a small helper:

import pTimeout from 'p-timeout'

const addTimeout = (onMessage, delay) => function () {
  return pTimeout(onMessage.apply(this, arguments), delay)
}

[huan]

@julien-f It's a brilliant way to set the timeout for the JSON RPC server side Peer.

However, I'm facing a situation that I can not set the timeout for the client-side Peer.

json-rpc-peer/src/index.js

Lines 138 to 145 in cd37a3d

	request(method, params) {
	return new Promise((resolve, reject) => {
	const requestId = nextRequestId++;
	this.push(format.request(requestId, method, params));
	this._deferreds[requestId] = { resolve, reject };
	});

According to the above code, if my server will not response me, then it seems that I have no way to control my request() to fail after a period of time?