How can I publish Position in rviz ?

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Hello, I am new in ROS and I have a little question.

I want to publish a starting position and goal position on rviz but I didn't succeed. I don't know where is the error in my code and/or if it possible or not because I have seen no information about it on the internet.

This in ROS2 Foxy and I use the turtlebot3.

Thank you for your help, I let you my code here :

import rclpy
from rclpy.node import Node
from std_msgs.msg import String
from geometry_msgs.msg import PoseWithCovarianceStamped, PoseStamped


class MinimalPublisher(Node):

def __init__(self):
    super().__init__('minimal_publisher')
    self.publisher_ = self.create_publisher(PoseWithCovarianceStamped , '/initialpose', 10)
    self.pose_callback()
    self.publisher_ = self.create_publisher(PoseStamped , '/goal_pose', 10)
    self.goal_callback()

def pose_callback(self):
    self.msg = PoseWithCovarianceStamped()
    self.msg.header.frame_id = "/base_link"
    self.msg.pose.pose.position.x = 0.7
    self.msg.pose.pose.position.y = 0.5
    self.msg.pose.pose.position.z = 0.1
    self.publisher_.publish(self.msg)

def goal_callback(self):
    self.goal = PoseStamped()
    # self.msg.header.frame_id = "/base_link"
    self.goal.pose.position.x = 0.7
    self.goal.pose.position.y = 0.5
    self.goal.pose.position.z = 0.1
    self.publisher_.publish(self.goal)
    print("done")


def main(args=None):
    rclpy.init(args=args)
    minimal_publisher = MinimalPublisher()
    rclpy.spin(minimal_publisher)
    minimal_publisher.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
     main()