Do not start session if app is accessed by a bot

In my Node.js app I initialize session every time new client accesses the app by typical

app.use(express.session({ secret: config.secret.session, store: new RedisStore()));

which is inside app.configure.

Now what can I do if I do not want to filter traffic from bots and not create sessions if I detect that user-agent belongs to a bot by passing user-agent through a regex e.g.

/bot|index|spider|crawl|wget|slurp|Mediapartners-Google/i

But where do I put this condition?

I would use the file robots.txt like that:

User-agent: *
Disallow: /

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