Polka and Express have differing behaviours viz the order in which middlewares run — Express runs them in the order in which they're added (with app.use or app.get), but Polka appears to run middlewares with a basepath after middlewares without, regardless of the order in which they're added to the app.
To run...
yarn
node index.js
...then navigate to localhost:3000. Expected behaviour is to see a picture of a potato; actual behaviour is a 'not found' message.
To see the potato, run it with Express:
node index.js express