add comments

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
 }
 

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