fn start_leftwm_session(current_exe: &Path) -> Child {
    let worker_file = current_exe.with_file_name("leftwm-worker");

    Command::new(worker_file)
        .spawn()
        .expect("failed to start leftwm")
}
starts the leftwm session and returns the process/leftwm-session
leftwm/src/bin/leftwm.rs