Nodejs express session - not load session for static content?

I'm using express session like this inside my server.js and inside the app.configuire() block.

I want to use session only if there's some api calls but not in those static content loading as it seems it will extend session which I don't want.

So is there a way to specific not to use session for those static content? Thanks.

app.use(express.session({ secret: sessionVal }));