Session cookie refresh

Hello I'm using Firebase Auth (actually gcp identity platform) with the session cookie in a NextJS app, everything is working fine but I'm looking a way to refresh the cookie to avoid forcing the user to login again when the session expire. There isn't an official way to do that but I might have found a solution, I'm just not 100% sure this is secure enough or if there are issues I'm missing, the idea is to have a refresh endpoint with this code:

```
const idToken = req.cookies.session || req.body.sessionCookie;
const session = await auth().verifySessionCookie(idToken, true);

if (session) {
const customToken = await auth().createCustomToken(session.uid);

const response = await fetch(
`${GOOGLE_API}:signInWithCustomToken?key=${process.env.NEXT_PUBLIC_API_KEY}`,
{
method: "POST",
cache: "no-cache",
headers: { "Content-Type": "application/json" },
body: JSON.stringify({ token: customToken, returnSecureToken: true }),
},
);

const result = await response.json();
const sessionCookie = await auth().createSessionCookie(result.idToken, {
expiresIn,
});

setCookie(res, "session", sessionCookie, {
...cookieOptions,
maxAge: expiresIn,
});

return res.json({ session, customToken, sessionCookie });
}
```

then every time I want I can call this refresh endpoint and the session will be updated...it seems to work but I'd like to have some feedback on this.