New Google Sign-In API - refresh token

Problem

I am trying to use the New Google Sign-In API for authenticating with my own backend server. Every call to my server contains the idToken jwt as a Bearer token. On the backend side, I validate the token by checking the signature, and checking if the token is expired or not. The problem is that the New Google Sign-In API returns jwts with 1 hour expiration time, but I could not find any way to refresh the token.

Questions

1. Is this a valid/safe way to authenticate the user with my backend server?
2. How do I get a fresh id token without the user having to go through the sign-in flow again?

Code

How I get the idToken client side

fun showSignInDialog() {
  val request = GetSignInIntentRequest.builder()
    .setServerClientId(GOOGLE_SERVER_CLIENT_ID)
    .build()

  Identity.getSignInClient(context)
    .getSignInIntent(request)
    .addOnSuccessListener {
      googleSignInLauncher.launch(IntentSenderRequest.Builder(it).build())
    }
}

fun handleSignInResult(result: ActivityResult) {
  val credential = Identity.getSignInClient(context)
    .getSignInCredentialFromIntent(result.data)

  // later this token will be used for querying user-related data on my backend
  setToken(credential.googleIdToken)
}

How I validate my endpoints on the backend side

fun Application.installAuthentication() {
  val googleJwtIssuer = environment.config.property("jwt.google.domain").getString()
  val googleJwtAudience = environment.config.property("jwt.google.audience").getString()
  val jwtRealm = environment.config.property("jwt.google.realm").getString()
  val googleJwkProvider = JwkProviderBuilder(URL("https://www.googleapis.com/oauth2/v3/certs"))
    .cached(10, 24, TimeUnit.HOURS)
    .rateLimited(10, 1, TimeUnit.MINUTES)
    .build()
  install(Authentication) {
    jwt("google") {
      verifier(googleJwkProvider) {
        withIssuer(googleJwtIssuer)
        withAudience(googleJwtAudience)
      }
      realm = jwtRealm
      validate { credentials ->
        if (credentials.payload.audience.contains(googleJwtAudience))
          JWTPrincipal(credentials.payload)
        else
          null
      }
    }
  }
}

// in my main
installAuthentication()
routing {
  authenticate("google") {
    get("/get-todos") {
      val payload = call.principal<JWTPrincipal>()?.payload ?: error("JWTPrincipal not found")
      
      call.respond(getTodos(payload.subject))
    }
  }
}

Edit

Sample JWT returned by the google sign in API (on first sign in)

{
  "iss": "https://accounts.google.com",
  "azp": "secret",
  "aud": "secret",
  "sub": "secret",
  "email": "secret@gmail.com",
  "email_verified": true,
  "name": "Ben Jerry",
  "picture": "https://lh3.googleusercontent.com/secret",
  "given_name": "Patrik",
  "family_name": "Aradi",
  "locale": "en-GB",
  "iat": 1616243551,
  "exp": 1616247151
}

It does not have a refresh token in it unfortunatelly