Go: refactor (#16602)

### Summary

1. update doc
2. refactor route code

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

internal/binding/cpp/term.cpp

@@ -0,0 +1,24 @@
+// Copyright(C) 2023 InfiniFlow, Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "term.h"
+
+std::string PLACE_HOLDER("<PH>");
+
+void Term::Reset() {
+    text_.clear();
+    word_offset_ = 0;
+}
+
+Term TermList::global_temporary_;