Reproducing the error (with next@7.0,2)

1. npm install
2. npm run dev

Error dissapears with next@6.1.1

1. npm install next@6.1.1
2. npm run dev
3. Everying works as expected

Resolved

Please visit webpack/webpack#6642 for more information in the mean time

in your next.config.js

const withWorkers = require("@zeit/next-workers");
module.exports = withWorkers({
  webpack(config, options) {
    // add this to make the web workers work in next js version 7
    config.output.globalObject = `(typeof self !== 'undefined' ? self : this)`;
    return config;
  }
});

and the error goes away :)