Duplicate RPC callback and unnecessary lock in RequestResponseFuture

[Gordon Wang]

BUG REPORT

1. Should only invoke callback when rrf is timout, as in Java client, or the callback will be called twice when RPC is finished normally:
   

   rocketmq-client-go/internal/request_response_future.go

   Lines 54 to 57 in 6c77b67

    if rrf.IsTimeout() { 
    	rrf.CauseErr = fmt.Errorf("correlationId:%s request timeout, no reply message", s) 
    } 
    rrf.ExecuteRequestCallback() 

https://github.com/apache/rocketmq/blob/e7f29798ece70e218f7233a7ec85f01e8706a062/client/src/main/java/org/apache/rocketmq/client/producer/RequestFutureHolder.java#L67

2. Since we already use chan Done to sync the write and read of response message, there is no need to use mutex:
   

   rocketmq-client-go/internal/request_response_future.go

   Lines 133 to 145 in 6c77b67

    	case <-rf.Done: 
    		rf.mtx.RLock() 
    		rf.mtx.RUnlock() 
    		return rf.ResponseMsg, nil 
    	} 
    } 
     
    func (rf *RequestResponseFuture) PutResponseMessage(message *primitive.Message) { 
    	rf.mtx.Lock() 
    	defer rf.mtx.Unlock() 
    	rf.ResponseMsg = message 
    	close(rf.Done) 
    } 

3. Consider edge cases, we should add non-blocking check of chan Done before calculate timeout, to avoid any possibility of duplicate callback:
   

   rocketmq-client-go/internal/request_response_future.go

   Lines 147 to 150 in 6c77b67

    func (rf *RequestResponseFuture) IsTimeout() bool { 
    	diff := time.Since(rf.BeginTime) 
    	return diff > rf.Timeout 
    }