http://wiki.ros.org/actionlib/DetailedDescription
Calling Actions from a SMACH state machine
The goal messages and action interfaces for states…
http://wiki.ros.org/smach/Tutorials/Calling%20Actions
http://wiki.ros.org/actionlib/DetailedDescription#Threading%20Model%20(C++) – Threading
Simple Action Client – Doxygen
http://docs.ros.org/melodic/api/actionlib/html/classactionlib_1_1SimpleActionClient.html
Simple Action Server – Doxygen
http://docs.ros.org/melodic/api/actionlib/html/classactionlib_1_1SimpleActionServer.html
http://docs.ros.org/melodic/api/actionlib/html/simple__action__server__imp_8h_source.html
actionlib_msgs/GoalStatus
http://docs.ros.org/melodic/api/actionlib_msgs/html/msg/GoalStatus.html