TypeError: Cannot set property 'oauthRequestToken' of undefined when using sample code from readme

[joshbalfour]

I copied the sample code from the readme and got this error:

/Users/joshuabalfour/Projects/iot-project/node_modules/flutter/src/Flutter.js:128
    req.session.oauthRequestToken = token;
                                  ^
TypeError: Cannot set property 'oauthRequestToken' of undefined
    at /Users/joshuabalfour/Projects/iot-project/node_modules/flutter/src/Flutter.js:128:35
    at /Users/joshuabalfour/Projects/iot-project/node_modules/flutter/node_modules/oauth/lib/oauth.js:551:7
    at passBackControl (/Users/joshuabalfour/Projects/iot-project/node_modules/flutter/node_modules/oauth/lib/oauth.js:390:11)
    at IncomingMessage.<anonymous> (/Users/joshuabalfour/Projects/iot-project/node_modules/flutter/node_modules/oauth/lib/oauth.js:409:9)
    at IncomingMessage.emit (events.js:129:20)
    at _stream_readable.js:908:16
    at process._tickCallback (node.js:355:11)

I fixed it by requiring and using express-session in my app