what happend if i don'nt use 'haltOnTimedout' in express middleware 'connect-timeout'?

I'm new to express, I don'nt understand this connect-timeout middleware. Please visit this website: https://github.com/expressjs/timeout When using this as top-level,why I must use 'haltOnTimedout'? What happend if I donn't use it? I have already tried the below:

app.get('/', function(req, res, next) {
    console.log('/')
})

But I still puzzled. Who can explain me, thanks in advance!

via vcxiaohan