fix:The specified topic does not take effect when run the command:go run main.go produce/consume (#26)

diff --git a/examples/producer.go b/examples/producer.go
index 01e8105..e1c4d2f 100644
--- a/examples/producer.go
+++ b/examples/producer.go
@@ -40,7 +40,7 @@
 	fmt.Printf("Producer: %s started... \n", producer)
 	for i := 0; i < *amount; i++ {
 		msg := fmt.Sprintf("%s-%d", *body, i)
-		result, err := producer.SendMessageSync(&rocketmq.Message{Topic: "test", Body: msg})
+		result, err := producer.SendMessageSync(&rocketmq.Message{Topic: *topic, Body: msg})
 		if err != nil {
 			fmt.Println("Error:", err)
 		}
diff --git a/examples/push_consumer.go b/examples/push_consumer.go
index 723e32f..38e434c 100644
--- a/examples/push_consumer.go
+++ b/examples/push_consumer.go
@@ -34,7 +34,7 @@
 	ch := make(chan interface{})
 	var count = (int64)(*amount)
 	// MUST subscribe topic before consumer started.
-	consumer.Subscribe("test", "*", func(msg *rocketmq.MessageExt) rocketmq.ConsumeStatus {
+	consumer.Subscribe(*topic, "*", func(msg *rocketmq.MessageExt) rocketmq.ConsumeStatus {
 		fmt.Printf("A message received: \"%s\" \n", msg.Body)
 		if atomic.AddInt64(&count, -1) <= 0 {
 			ch <- "quit"