(examples) Do not throw in async flows

[XVincentX]

Hey,
I was just having a look to this plugin and, reading the example, I noticed this:

fastify.register(require('fastify-mongodb'), {
  url: 'mongodb://mongo/db'
}, err => {
  if (err) throw err
})

Throwing in in async flow is an antipattern, it will probably crash your entire process as nobody can catch that exception. While it's just an example, you might want to write a different code to handle the error.

P.S: The same goes in the listen function below.

[delvedor]

Throw in that callback will crash your process :)
The error handling is demanded to the user, it is your choice how handle it.

[XVincentX]

The error handling is demanded to the user, it is your choice how handle it.

I know, I was just thinking that's is wrong to put it there; a good console.error in case of any error would probably be better, but it's your call.

[delvedor]

It definitely depends on your code, for example, you have a web service that needs mongodb, without it cannot work.
What you do is try to connect to mongo with this plugin and if you can't, throw an error.

Don't forget that the callback is executed at bootstrap time, so if it have to crash, it will do it when you open up the server, not at "runtime" :)

[XVincentX]

I disagree but ok, I got your point.

[mcollina]

The correct approach is not to place any callback there. The default behavior in case of error is well defined (it will emit an 'error' event on the server). We just need to update the README.

Placing console.error(err) there are wrong in both cases, as those are fatal and not-recoverable errors for the demo script.