Improve typesafety of your next/router

types.d.ts

import { NextRouter } from "next/router";

declare module "next/router" {
  export type Locale = "en" | "nl" | "de";
  export function useRouter(): Omit<NextRouter, "locale" | "locales"> & {
    locale: Locale;
    locales: Locale[];
  };
}