** I want to build an action client, but I find that when the program runs to the statement of building the client, it doesn't continue to execute. I don't know what happened. The program does not report errors and can be compiled normally. The program is blocked here: "client (nh," actiontrajectorydemo ", true);"

This is my code：**

 typedef actionlib::SimpleActionClient<control_msgs::FollowJointTrajectoryAction> Client;

int main(int argc, char *argv[])
{
    ROS_INFO("action client...");
    ros::init(argc,argv,"action_trajectory_client");
    ros::NodeHandle nh;
    std::cout << "ok-1" << std::endl;
    Client client(nh,"action_trajectory_demo",true); //The program is blocked here！！！！

    control_msgs::FollowJointTrajectoryGoal action_goal;
    rosbag::Bag bag;
    bag.open("trajectory.bag", rosbag::bagmode::Read);

    rosbag::View view(bag, rosbag::TopicQuery("/robotic_arm_controller/follow_joint_trajectory/goal"));
    foreach(rosbag::MessageInstance const m, view)
    {

        control_msgs::FollowJointTrajectoryActionGoal::ConstPtr s = m.instantiate<control_msgs::FollowJointTrajectoryActionGoal>();//control_msgs/FollowJointTrajectoryGoal
        if (s != NULL) //std_msgs::Int32::ConstPtr
        {
            action_goal = s->goal;
            //std::cout << action_goal.trajectory.joint_names[2] << std::endl; 
            std::cout << "send goal..." << std::endl; 
            client.sendGoal(action_goal,&done_cb,&active_cb,&feedback_cb);//向服务端发送goal  

        }else
        {
            std::cout << "null" << std::endl;
        }
    }
    bag.close();
    ros::spin();
    return 0;

}