The Next.js team has an official plugin being developed, while plugin supports it's still in canary only, the way the plugin works it's simpler than next-ga and I recommend you to check it and do it manually in your project until it's stable.
Plugin link: https://github.com/zeit/next.js/tree/canary/packages/next-plugin-google-analytics
Next.js High Order Component to integrate Google Analytics on every page change.
Install it
yarn add next-ga
Import it inside your pages/_app.js
;
import Router from "next/router";
import withGA from "next-ga";
Wrap your custom App container with it
// pass your GA code as first argument
export default withGA("UA-xxxxxxxxx-1", Router)(MyApp);
That's it, now when the user access a page it will log a pageview to Google Analytics, each page change after that will also trigger a pageview on Google Analytics.
Note: This module detects if it's running in localhost and do nothing there to avoid polluting your analytics with local data.