Next.js getServerSideProps redirection ERR_HTTP_HEADERS_SENT error

I'm trying to make a private page with Next.js.

I wrote pages/private.tsx.

import React from 'react';
import { Label } from '@components/atoms';
import { Layout } from '@components/Layout';
import Link from 'next/link';
import { GetServerSideProps } from 'next';

const Private = (props: any) => {
  console.log(props);
  return (
    <Layout>
      <Link href="/">
        <a>
          <Label size="L1" margin="32px 0 0 24px" pointer>
            Go Back to Home
          </Label>
        </a>
      </Link>
    </Layout>
  );
};

export const getServerSideProps: GetServerSideProps = async (ctx) => {
  // redirect test: always redirect to '/login'
  ctx.res.setHeader('Location', '/login');
  ctx.res.statusCode = 302;
  ctx.res.end();
  return {
    props: {},
  };
};

export default Private;

It works well. If I try to go /private, it redirects to /login.

Browser is OK, but my console said,

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:526:11)
    at DevServer.sendHTML (Directory/node_modules/next/server/next-dev-server.ts:663:9)
    at DevServer.render (Directory/node_modules/next/next-server/server/next-server.ts:1232:17)
    at Object.fn (Directory/node_modules/next/next-server/server/next-server.ts:726:11)
    at Router.execute (Directory/node_modules/next/next-server/server/router.ts:247:24)
    at DevServer.run (Directory/node_modules/next/next-server/server/next-server.ts:1158:23)
    at DevServer.handleRequest (Directory/node_modules/next/next-server/server/next-server.ts:551:14) {
  code: 'ERR_HTTP_HEADERS_SENT'
}

The reason I think is after the server sent response to browser, I tried to send 302 status code again.

Is there a way to fix this error?

++ I tried to make redirection code in Client-Side, but it shows private page for a second and redirected. I want to block in the initial loading.