NodeJS: How to pass variables from a POST request to a GET request?

I’m trying to pass in some data I’ve received from my POST request to be utilized inside my GET request as shown below:

app.post('/genre/non-fiction', (req, res, next) => {
  let received_data = req.body.myData;
});   

app.get('/genre/non-fiction/:id/read', (req, res) => {
   res.send("Hello World");
});

I’ve found this solution from this article that explains how to pass variables from one middleware to another using next(), and so I tried something like this:

app.post('/genre/non-fiction', (req, res, next) => {
  let received_data = req.body.myData;
  req.pass_data = received_data;
  next();
});    

// I've also tried passing the "recieved_data" variable into the middleFunction, but that doesn't do anything either.

function middleFunction(req, res, next) {
    console.log(req.pass_data);
    next();
}

app.get('/genre/non-fiction/:id/read', middleFunction, (req, res) => {
    res.send(req.pass_data);
});

When attempting to test it out, nothing shows up on the page. I’ve also console.logged the pass_data variable inside the GET request, but it returns undefined.

Any help would be greatly appreciated!