diff --git a/pool.go b/pool.go
index ac575b8..77ec952 100644
--- a/pool.go
+++ b/pool.go
@@ -52,7 +52,10 @@ type Pool struct {
 
 	// lock for synchronous operation.
 	lock sync.Mutex
+
+	// cond for waiting idle worker
 	cond *sync.Cond
+
 	once sync.Once
 }
 
diff --git a/pool_func.go b/pool_func.go
index 074710e..fc3c73f 100644
--- a/pool_func.go
+++ b/pool_func.go
@@ -50,7 +50,10 @@ type PoolWithFunc struct {
 
 	// lock for synchronous operation.
 	lock sync.Mutex
+
+	// cond for waiting idle worker
 	cond *sync.Cond
+
 	// pf is the function for processing tasks.
 	poolFunc pf