internal FineBstNode<TK, TV> Find(TK key)
        {
            var cur = Root;
            cur?.FineMutex.WaitOne();
            while (cur != null)
            {
                switch (cur.Key.CompareTo(key))
                {
                    //Eq
                    case 0:
                        cur.FineMutex.ReleaseMutex();
                        return cur;
                    //Greater
                    case 1:
                        cur.Left?.FineMutex.WaitOne();
                        cur.FineMutex.ReleaseMutex();
                        cur = cur.Left;
                        break;
                    // Less
                    case -1:
                        cur.Right?.FineMutex.WaitOne();
                        cur.FineMutex.ReleaseMutex();
                        cur = cur.Right;
                        break;
                }
            }

            return null;
        }