The example in the npm page shows this:

express.get('/', asyncHandler(async (req, res, next) => {

    const bar = await foo.findAll();

    res.send(bar)

}))

Without asyncHandler you'd need:

express.get('/',(req, res, next) => {

    foo.findAll()

    .then ( bar => {

       res.send(bar)

     } )

    .catch(next); // error passed on to the error handling route

})

The first one uses the async / await language elements and is more concise.