After pushconsumer is forcibly closed and restarted again, the previously consumed messages will be re-consumed

**code is this：**
// consume message
int doConsumeMessage(struct CPushConsumer *consumer, CMessageExt *msgExt)
{
cout << "[Consume Message] " << "MsgTopic:" << GetMessageTopic(msgExt) << ", MsgTags:" << GetMessageTags(msgExt)
<< ", MsgKeys:" << GetMessageKeys(msgExt) << ", MsgBody:" << GetMessageBody(msgExt) << endl;

return E_CONSUME_SUCCESS;
}

int main(int argc, char *argv[])
{
cout << "Push consumer Initializing...." << endl;
// create push consumer and set some values for it
CPushConsumer *consumer = CreatePushConsumer("Group_Consumer_Test");
SetPushConsumerNameServerAddress(consumer, "192.168.159.202:5432");
Subscribe(consumer, "canal_manager", "*");
// register message callback
RegisterMessageCallback(consumer, doConsumeMessage);
// start push consumer
StartPushConsumer(consumer);
cout << "Push consumer start, and listening message within 1min..." << endl;
for (int i = 0; i < 6; i++)
{
cout << "Already Running: " << (i * 10) << "S" << endl;
usleep(10000000);
}
// shutdown push consumer
ShutdownPushConsumer(consumer);
// destroy push consumer
DestroyPushConsumer(consumer);
cout << "PushConsumer Shutdown!" << endl;

return 0;
}

**After pushconsumer is forcibly closed and restarted again, the previously consumed messages will be re-consumed**