How could it be possible for a route that establishes a connection to a GrapgQL subscription to be able to inspect the header and update the req.data(...) (like in graphql_handler)before establishing a connection to the subscription?

Here is my router:

    use async_graphql_axum::{GraphQLRequest, GraphQLResponse, GraphQLSubscription};
    // Other imports ...
    
    async fn graphql_handler(
        schema: Extension<SchemaRoot>,
        headers: HeaderMap,
        req: GraphQLRequest,
    ) -> GraphQLResponse {
        let mut req = req.into_inner();
    
        if let Some(value) = headers.get("some-header") {
           // ...
        }
    
        return schema.execute(req.data(headers)).await.into();
    }
    
    pub fn router<S>(schema: SchemaRoot) -> Router<S>
    where
        S: Clone + Send + Sync + 'static,
    {
        Router::new()
            .route(
                "/graphql",
                post(graphql_handler).get_service(GraphQLSubscription::new(schema)),
            )
    }

Right now this works as a get_service, but I need to be able to check some headers and update the req.data(...) before setting up the subscription.