const handler = (): Response => {
  console.log("Hello world!");
  const data = { hello: "world" };
  return Response.json({ data });
};

const api = Api();
api.post(handler);

export async function POST(request: NextRequest, ctx: ApiRequestContext) {
  return api.run(request, ctx);
}

Type error: Route "src/app/api/waitlist/route.ts" has an invalid export:
  "Promise<unknown>" is not a valid POST return type:
    Expected "void | Response | Promise<void | Response>", got "Promise<unknown>".
      Expected "Promise<void | Response>", got "Promise<unknown>".
        Expected "void | Response", got "unknown".

export async function POST(request: NextRequest, ctx: ApiRequestContext) {
   return api.run(request, ctx) as Promise<any>;
}