Function lock_session 

pub fn lock_session(
    root: &Path,
    id: &str,
    wait: Duration,
) -> Option<SessionLock>

Takes the lock of a session by creating {session_id}.lock exclusively, polling for up to wait. None when the lock stays held, or the id or the folder is unusable. A lock file older than the hook timeout belongs to a hook that died, and the next caller takes it over.