title: mg_wakeup_server_ex ( ) callback not getting called while using mongoose 5.4
body: <p>I am working with mongoose 5.4
  Below are the lines of code</p>
  
  <pre><code>char* eventToOCC = NULL;
  
  static int websocket_data_push(struct mg_connection *conn, enum mg_event ev)
  {
      if ((ev == MG_POLL) &amp;&amp; (NULL != conn-&gt;uri) &amp;&amp; (NULL != eventToOCC))
      {
          if (strcmp(conn-&gt;uri, "/web") == 0 &amp;&amp; conn-&gt;is_websocket) {
              mg_websocket_printf(conn, WEBSOCKET_OPCODE_TEXT, "%s",
                                  eventToOCC);
          }
      }
      return MG_FALSE;
  }
  
  
  void SampleClass::sendEventsToClinet(char* evString)
  {
      if(evString != NULL)
      {
          eventToOCC = evString;
          printf("EVENT SENT is ---%s---\n",evString);
          mg_wakeup_server_ex(mgserver, websocket_data_push, "%lu %s",
                              (unsigned long) time(NULL), (const char *) evString);
      }
      else
      {
          printf("Connection Pointer is NULL\n");
      }
      return ;
  }
  </code></pre>
  
  <p>Here, the callback is not getting called whenever mg_wakeup_server_ex() is invoked. 
  I don't suspect c++ method calling a C Method because it works in few cases.
  Only at certain places, the websocket_data_push () callback doesnt get called.
  Could you please help !!!</p>