334_C++_std::bind中使用shared_from_this()
std::bind(&HttpClient::getPwd, shared_from_this(), std::placeholders::_1, std::placeholders::_2)；[ HttpClient继承自NetObj，NetObj是父类，NetObj受到std::shared_pt
std::bind(&HttpClient::getPwd, shared_from_this(), std::placeholders::_1, std::placeholders::_2)；[ HttpClient继承自NetObj，NetObj是父类，NetObj受到std::shared_pt