Update about-connection-context.md (#1688)

docs/about-connection-context.md

@@ -19,6 +19,8 @@ http协议可以说是一种完全无连接状态的协议，http会话，是通
 事务型mysql，可以固定连接，这部分内容请参考mysql相关文档。  
 但是，如果我们实现一个redis协议的server，那我们需要知道当前连接上的状态了。  
 
+此外，我们还可以通过连接上下文件被释放的事件来感知连接被远端关闭。
+
 # 使用连接上下文的方法
 
 我们需要强调的是，一般情况下只有server任务需要使用连接上下文，并且只需要在process函数内部使用，这也是最安全最简单的用法。  
@@ -40,12 +42,16 @@ class WFConnection : public CommConnection
 public:
     void *get_context() const;
     void set_context(void *context, std::function<void (void *)> deleter);
+    void set_context(void *context);
     void *test_set_context(void *test_context, void *new_context,
                            std::function<void (void *)> deleter);
+    void *test_set_context(void *test_context, void *new_context);
 };
 ~~~
 get_connection()只可在process或callback里调用，而且如果callback里调用，需要检查返回值是否为NULL。  
-如果成功取得WFConnection对象，就可以操作连接上下文了。连接上下文是一个void *指针，在连接被关闭时，deleter被自动调用。  
+如果成功取得WFConnection对象，就可以操作连接上下文了。连接上下文是一个void *指针。  
+设置连接上下文可以同时传入deleter函数，在连接被关闭时，deleter被自动调用。    
+如果调用无deleter参数的接口，可以只设置新的上下文，保持原有的deleter不变。  
 
 # 访问连接上下文的时机和并发问题
 

docs/en/about-connection-context.md

@@ -20,6 +20,8 @@ Due to this limitation, in the framework, you cannot use the SELECT command of R
 Transactional MySQL tasks can use fixed connections. Please see MySQL documentations for relevant details.   
 However, if you implement a server based on Redis protocol, you need to know the current connection status.
 
+By using the deleter function of connection context, users can also get notified when the connection was closed by the peer.
+
 # How to use connection context
 
 Note: generally, only the server tasks need to use the connection context, and the connection context is used only inside the process function, which is also the safest and simplest.   
@@ -44,13 +46,15 @@ class WFConnection : public CommConnection
 public:
     void *get_context() const;
     void set_context(void *context, std::function<void (void *)> deleter);
+    void set_context(void *context);
     void *test_set_context(void *test_context, void *new_context,
                            std::function<void (void *)> deleter);
+    void *test_set_context(void *test_context, void *new_context);
 };
 ~~~
 
 **get\_connection()** can only be called in a process or a callback. If you call it in the callback, please check whether the return value is NULL.   
-If you get the WFConnection object successfully, you can perform operations on the connection context. A connection context is a void \* pointer. When the connection is closed, the deleter is automatically called.
+If you get the WFConnection object successfully, you can perform operations on the connection context. A connection context is a void \* pointer. When the connection is closed, the deleter is automatically called. When using the setting context functions without ``deleter`` argument, the original deleter will be kept unchanged.
 
 # Timing and concurrency for accessing connection context