How to use the next-server/dist/server/router.route function in next-server

async addExportPathMapRoutes () {
    // Makes `next export` exportPathMap work in development mode.
    // So that the user doesn't have to define a custom server reading the exportPathMap
    if (this.nextConfig.exportPathMap) {
      console.log('Defining routes from exportPathMap')
      const exportPathMap = await this.nextConfig.exportPathMap({}, {dev: true, dir: this.dir, outDir: null, distDir: this.distDir, buildId: this.buildId}) // In development we can't give a default path mapping
      for (const path in exportPathMap) {
        const {page, query = {}} = exportPathMap[path]

        // We use unshift so that we're sure the routes is defined before Next's default routes
        this.router.add({
          match: route(path),
          fn: async (req, res, params, parsedUrl) => {
            const { query: urlQuery } = parsedUrl

            Object.keys(urlQuery)
              .filter(key => query[key] === undefined)
              .forEach(key => console.warn(`Url defines a query parameter '${key}' that is missing in exportPathMap`))

            const mergedQuery = {...urlQuery, ...query}

            await this.render(req, res, page, mergedQuery, parsedUrl)
          }
        })
      }
    }
  }

generateRoutes () {
    const routes = super.generateRoutes()

    // In development we expose all compiled files for react-error-overlay's line show feature
    // We use unshift so that we're sure the routes is defined before Next's default routes
    routes.unshift({
      match: route('/_next/development/:path*'),
      fn: async (req, res, params) => {
        const p = join(this.distDir, ...(params.path || []))
        await this.serveStatic(req, res, p)
      }
    })

    return routes
  }