ROS2 action goal canceling problem

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action canceling example: https://github.com/ros/ros_tutorials/...

You can use the following structure for an action server/client.

https://github.com/ros2/rclpy/blob/galactic/rclpy/rclpy/action/server.py#L185

https://github.com/ros2/rclpy/blob/galactic/rclpy/rclpy/action/client.py#L111

import rclpy
from rclpy.node import Node
from rclpy.action import ActionServer
from rclpy.action import CancelResponse
from rclpy.action import ActionClient
from action_tutorials_interfaces.action import Fibonacci

class MyActionServer(Node):
    def __init__(self):
        super().__init__("my_action_server")
        self._action_server = ActionServer(
            self,
            Fibonacci,
            'fibonacci',
            self.execute_callback,
            cancel_callback=self.cancel_callback,
        )

    def execute_callback(self, goal_handle):
        return Fibonacci.Result()

    def cancel_callback(self, cancel_request):
        return CancelResponse.ACCEPT


class MyActionClient(Node):
    def __init__(self):
        super().__init__("my_action_client")
        self._action_client = ActionClient(self, Fibonacci, 'fibonacci')

    def send_goal(self):
        #Send an action goal
        goal_msg = Fibonacci.Goal()
        self._action_client.wait_for_server()
        future = self._action_client.send_goal_async(goal_msg)
        future.add_done_callback(self.goal_response_callback)

    def goal_response_callback(self, future):
        self.goal_handle = future.result()
        if not goal_handle.accepted:
            self.get_logger().info('Goal rejected :(')
            return

        self.get_logger().info('Goal accepted :)')

        self._get_result_future = goal_handle.get_result_async()

    def cancel_goal(self):
        self.get_logger().info('Canceling goal')
        future = self.goal_handle.cancel_goal_async()
        future.add_done_callback(self.goal_canceled_callback)

    def goal_canceled_callback(self, future):
        cancel_response = future.result()
        if len(cancel_response.goals_canceling) > 0:
            self.get_logger().info('Cancelling of goal complete')
        else:
            self.get_logger().warning('Goal failed to cancel')