Issue with ros::Time when using /use_sim_time

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Hello everyone,

I have the following issue that ros::Time::now()` always returns zero using the following minimum example.

#include <ros/ros.h>

int main(int argc, char **argv)
{
      ros::init(argc, argv, "force_test_trajectory_pub");     // create ROS node
      while(ros::ok())  {
            beginTime = ros::Time::now();
            ROS_INFO("Starting time %f", beginTime.toSec());
      }
}

The following things are running propperly:

• I first start roscore as usual
• Then I set the parameter /use_sim_time to true
• Then I run gazebo using rosrun gazebo_ros gazebo to get a clock published on /clock
• Then I run the example above but which only outputs 0 even though /clock is constantly publishing

When I pause Gazebo, the while loop stops as well, which means synchronization is working in some way.

Do you have any suggestion how to fix this problem?