https://github.com/luceneplusplus/LucenePlusPlus/pull/227

diff --git a/src/core/util/ThreadPool.cpp b/src/core/util/ThreadPool.cpp
index ee6640b..38f4170 100644
--- a/src/core/util/ThreadPool.cpp
+++ b/src/core/util/ThreadPool.cpp
@@ -30,6 +30,7 @@ ThreadPool::ThreadPool()
 }
 
 ThreadPool::~ThreadPool() {
+    io_context.stop();
     threadGroup.join_all(); // wait for all competition
 }