There can be confusion because in the turtlebot3_core the goal_velocity[2] array is given with [LINEAR=0] and [ANGULAR=1] and in the turtlebot3_motor_driver it was received with [LEFT=0] and [RIGHT=1].
Alternative is to define LINEAR 0 and ANGULAR 1 in the turtlebot3_motor_driver.h.
A little detail who can help understanding the code.
There can be confusion because in the turtlebot3_core the goal_velocity[2] array is given with [LINEAR=0] and [ANGULAR=1] and in the turtlebot3_motor_driver it was received with [LEFT=0] and [RIGHT=1]. Alternative is to define LINEAR 0 and ANGULAR 1 in the turtlebot3_motor_driver.h.
A little detail who can help understanding the code.