feat: increase the default value of pingTimeout

This value was updated from 60000 to 5000 in [1], included in
`[email protected]` (Feb 2018).

The reasoning back then:

Some users experienced long delays between disconnection on the
server-side and on the client-side. The "disconnect" event would take a
long time to fire in the browser, probably due to a timer being
delayed. Hence the change.

That being said, the current value (5s) now causes unexpected
disconnections when a big payload is sent over a slow network, because
it prevents the ping-pong packets from being exchanged between the
client and the server. This can also happen when a synchronous task
blocks the server for more than 5 seconds.

The new value (20s) thus seems like a good balance between quick
disconnection detection and tolerance to various delays.

Note: pingInterval + pingTimeout is still below the threshold of React
Native, which complains if a timer is set with a delay of more than 1
minute.

[1]: 65b1ad1

Related:

- socketio/socket.io#2770
- socketio/socket.io#2769
- socketio/socket.io#3054
- socketio/socket.io#3376

README.md

@@ -222,7 +222,7 @@ to a single process.
  - `Object`: optional, options object
  - **Options**
  - `pingTimeout` (`Number`): how many ms without a pong packet to
- consider the connection closed (`5000`)
+ consider the connection closed (`20000`)
  - `pingInterval` (`Number`): how many ms before sending a new ping
  packet (`25000`)
  - `upgradeTimeout` (`Number`): how many ms before an uncompleted transport upgrade is cancelled (`10000`)

lib/server.js

@@ -23,7 +23,7 @@ class Server extends EventEmitter {
  this.opts = Object.assign(
  {
  wsEngine: process.env.EIO_WS_ENGINE || "ws",
- pingTimeout: 5000,
+ pingTimeout: 20000,
  pingInterval: 25000,
  upgradeTimeout: 10000,
  maxHttpBufferSize: 1e6,