prepare Ubuntu20.04
mkdir -p ~/catkin_ws/src
cd ~/catkin_ws
catkin init
cd ~/catkin_ws/src
git clone https://github.com/project-srs/ros_lecture.git
cd ~/catkin_ws/src/ros_lecture
git submodule update --init --recursive
rosdep install -i -y --from-paths ./
cd ~/catkin_ws
catkin build
see Qiita Page