Am I not using notifyFinish right?

finisher.py

from twisted.internet import defer
from klein import Klein

class App(object):

    app = Klein()

    @app.route('/')
    def index(self, request):
        def finished(x):
            print 'finished'
            return x
        request.notifyFinish().addBoth(finished)
        return 'hey\n'

    @app.route('/linger')
    def linger(self, request):
        def finished(x):
            print 'finished'
            return x
        request.notifyFinish().addBoth(finished)
        return defer.Deferred()


if __name__ == '__main__':
    App().app.run('127.0.0.1', 6000)

interaction

$ curl http://127.0.0.1:6000/
hey
$ curl http://127.0.0.1:6000/linger
^C
$ curl --max-time 3 http://127.0.0.1:6000/linger
curl: (28) Operation timed out after 3001 milliseconds with 0 bytes received

stdout

$ python finisher.py 
2016-08-18 13:59:02-0600 [-] Log opened.
2016-08-18 13:59:02-0600 [-] Site starting on 6000
2016-08-18 13:59:02-0600 [-] Starting factory <twisted.web.server.Site instance at 0x10a7458c0>
2016-08-18 13:59:03-0600 [-] "127.0.0.1" - - [18/Aug/2016:19:59:03 +0000] "GET / HTTP/1.1" 200 4 "-" "curl/7.50.0"
2016-08-18 13:59:03-0600 [-] finished