Timeout checks after x milliseconds

[jdelight]

Arguably this could be in the calling code however it might be nice to centralise it and provide a config interface.

For example, checks must run within 200ms by default but you can specify a custom timeout in the check object. Perhaps failing to run within the timeout calls the warning callback?

const postgresCheck = {
    name: 'postgres',
    check: (ok, warning, critical) => {
        pg.query.raw('SELECT version();', [])
            .then(ok)
            .catch(critical);
    },
    timeout: 500 // check needs a little longer than the default to run
};

Overall goal here is to prevent a request from waiting indefinitely if theres a problem with the check code itself.