ROS2 Subscription Callback not called with GAZEBO

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Hello,

I am having a problem on my first ROS2 node. I setup the turtlebot3 packages using this link (only Remote PC since I don't have a robot). Started the GAZEBO simulation using these instructions. After I run ros2 launch turtlebot3_gazebo empty_world.launch.py I can do ros2 topic echo /scan and receive data.

After this I created a colcon pkg using this tutorial and wrote following code:

import rclpy   
from rclpy.node import Node   
from sensor_msgs.msg import LaserScan   

class Platooning(Node):
    def __init__(self):
        # ROS Stuff #
        super().__init__("platooning")
        self.get_logger().info("Started init Node")
        self.sub_lidar = self.create_subscription(LaserScan, "/scan", self.lidar_callback, 10)
        self.get_logger().info("Finished init node {}".format(self.get_name()))
    def lidar_callback(self, msg):
        print("Callback")
        self.get_logger().info("I heard: {}".format(msg))

def main(args=None):
    rclpy.init(args=args)
    control = Platooning()
    try:
        while(1):
            rclpy.spin(control)
    except Exception as e:
        print("Exception: {}".format(e))
    control.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

I build the package using colcon build --symlink-install --packages-select platooning and start it using ros2 run platooning main.

The lidar_callback functions does not print anything using just gazebo, but as soon as I do ros2 topic pub /scan sensor_msgs/msg/LaserScan -1 the lidar_callback is executed.

Can somebody please help me?