We already implemented the worker in the JSON-RPC example. In the gRPC version, we use have same code, but expect a Receiver value and don't spawn a new thread:

fn worker_loop(receiver: Receiver<Action>) -> Result<(), Error> {
    let next = env::var("NEXT")?.parse()?;
    let remote = Remote::new(next)?;
    let mut in_roll_call = false;
    for action in receiver.iter() {
        match action { /* Action variants here */ }
    }
    Ok(())
}

Let's compile and run this example.