diff --git a/libgo/coroutine.h b/libgo/coroutine.h
index 946f43e0..d2751c7c 100644
--- a/libgo/coroutine.h
+++ b/libgo/coroutine.h
@@ -1,5 +1,6 @@
 #pragma once
 #define __const__
+#include <atomic>
 #include "common/config.h"
 #include "common/pp.h"
 #include "common/syntax_helper.h"
@@ -71,3 +72,29 @@ typedef ::co::CoTimer::TimerId co_timer_id;
 #define co_last_defer() ::co::GetLastDefer()
 #define co_defer_scope co_defer [&]
 
+class CountDownLatch {
+public:
+    explicit CountDownLatch(size_t n = 1) : mFlyingCount(n) {}
+
+    void Add(size_t i) {
+        mFlyingCount += i;
+    }
+
+    void Done() {
+        if (--mFlyingCount == 0) {
+            ch_0.Close();
+        }
+    }
+    void Wait() {
+        int done;
+        ch_0 >> done;
+    }
+private:
+    std::atomic<size_t> mFlyingCount;
+    co_chan<int> ch_0;
+
+    CountDownLatch(CountDownLatch const &) = delete;
+    CountDownLatch(CountDownLatch &&) = delete;
+    CountDownLatch& operator=(CountDownLatch const &) = delete;
+    CountDownLatch& operator=(CountDownLatch &&) = delete;
+};