Docker - Package not found even after source

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I'm trying to launch rosbridge_server inside docker.

This is my docker file:

FROM ros:noetic

RUN apt-get update && apt-get install -y \ 
    ros-noetic-rosbridge-server \
    ros-noetic-gps-common


RUN apt-get update && \
    rosdep update 

RUN apt-get update && apt-get install -y \
    lsof \
    python3-pip \
    ros-noetic-catkin 


ADD ./my_workspace /my_workspace

RUN /bin/bash -c 'source /opt/ros/noetic/setup.bash; \
        cd /my_workspace; catkin_make; \
        source /my_workspace/devel/setup.bash; \
        rospack find my_package'    #"rospack find" successfully prints my package's path. 
                                    #No problem here

#RUN rospack find my_package           #Here is the problem.
                                #If I uncomment this, I get an error that rospack is not found. 
                                       #It's like nor the source command or my package 
                                       #exist outside the previous RUN command

CMD ["./launch_ros_bridge.bash"] #Ros bridge is started but once 
                                 #I subscribe to a topic of my package,
                                 #it prints an error that "my_package" is not found

This is my launch_ros_bridge.bash script:

#!/bin/bash
roslaunch rosbridge_server rosbridge_websocket.launch

The error I receive when launch_ros_bridge.bash is executed, is

[-] [ERROR] [1624456872.953620]: [Client 0] advertise: Unable to import my_package.msg from package my_package. Caused by: No module named 'my_package'. [-] ROS path [0]=/opt/ros/noetic/share/ros [-] ROS path [1]=/opt/ros/noetic/share

Again, my package's path is not displayed.

My question is how can I successfully start and subscribe to ros bridge server inside a docker?