code: func (s *Store) SessionGet(ws memdb.WatchSet, sessionID string) (uint64, *structs.Session, error) {
  	tx := s.db.Txn(false)
  	defer tx.Abort()
  
  	// Get the table index.
  	idx := maxIndexTxn(tx, "sessions")
  
  	// Look up the session by its ID
  	watchCh, session, err := tx.FirstWatch("sessions", "id", sessionID)
  	if err != nil {
  		return 0, nil, fmt.Errorf("failed session lookup: %s", err)
  	}
  	ws.Add(watchCh)
  	if session != nil {
  		return idx, session.(*structs.Session), nil
  	}
  	return idx, nil, nil
  }
docs: // SessionGet is used to retrieve an active session from the state store.