next/server should not be imported outside of pages/_middleware.js

Question

I don't know why I am getting this error during the production build like npm run build

My project structure is like below

project/
       - src/
            - app
            - middleware.js

and the middleware file is like

export { default } from "next-auth/middleware";

export const config = {
    matcher: ["/listings/my-listings", "/listings/new"],
};

And when I try to build it. I encounter the following error:

Error: next/server should not be imported outside of pages/_middleware.js. See: https://nextjs.org/docs/messages/no-server-import-in-page @next/next/no-server-import-in-page

Optionally my API route is like below

import { NextResponse } from "next/server";
import { getCurrentUser } from "@/actions/getCurrentUser";

export async function POST(request) {
    const currentUser = await getCurrentUser();
    if (!currentUser) {
        return NextResponse.json(
            { message: "Authentication faild!" },
            { status: 401 }
        );
    }

    return NextResponse.json("okay");
}

I don't understand what is the issue here.

Thanks