I couldn't get session (OAuth & OIDC)

[soularium]

I'm converting express-session to next-auth using OIDC.

I have made a custom provider follow this and I can get id_token on server side.

https://next-auth.js.org/configuration/providers/oauth

Also, Server-side means custom callback function /api/auth/callback/sso.js which I have made.
So I have to check follow token is valid.

Debug.log(req.body.id_token);

And I have implemented follow this.

https://next-auth.js.org/getting-started/example

const { data: session } = useSession()

console.log(session)

but the session is null.
F12 network log is /api/auth/session -> 304..

How do I get the session information on client side?

or how do I set the session information on the server side?

I don't know what I'm missing.

======================= Update ================================

1. There is a nginx in front of nodejs app for ssl.
2. Attach code..

../api/auth/[...nextauth].js

import NextAuth from "next-auth";
import uuid from "uuid4";

export default NextAuth({
  providers: [
    {
      id: "sso",
      name: "sso",
      type: "oauth",
      idToken: true,
      wellKnown: process.env.ISSUER_URL,
      clientId: process.env.CLIENT_ID,
      clientSecret: process.env.CLIENT_SECRET,
      authorization: {
        params: {
          scope: "openid profile",
          response_type: "code id_token",
          response_mode: "form_post",
          nonce: uuid(),
          redirect_uri: process.env.REDIRECT_URI, // https://127.0.0.1/api/auth/callback/sso
        },
      },
    },
  ],
});

../api/auth/callback/sso.js

export default async (req, res) => {
  const { id_token } = req.body;

  console.log(id_token); // valid token.

  return res.redirect(process.env.NEXTAUTH_URL);
};

../pages/index.js

import { useSession, signIn, signOut } from "next-auth/react";

export default function Login() {
  const { data: session, status } = useSession();

  if (status === "loading") {
    return <div>loading...</div>;
  }
  console.log(session); // always null. and 304 after login success
  if (session) {
    return (
      <>
        Signed in as {session.user.email} <br />
        <button onClick={() => signOut()}>Sign out</button>
      </>
    );
  }
  return (
    <>
      Not signed in <br />
      <button onClick={() => signIn("sso")}>Sign in</button>
    </>
  );
}

../pages/_app.js

import "../styles/globals.css";
import { SessionProvider } from "next-auth/react";

function MyApp({ Component, pageProps: { session, ...pageProps } }) {
  console.log(pageProps);
  return (
    <SessionProvider session={session}>
      <Component {...pageProps} />
    </SessionProvider>
  );
}
export default MyApp;