main: starting worker threads
main: try_take...
main: try_take - would block (possibly empty)
main: put 1...
main: put 1
main: put 2...
main: put 2
main: put 3...
main: put 3
main: put 4...
main: put 4
main: put 5...
main: put 5
main: put 6...
main: put 6
main: put 7...
main: put 7
main: put 8...
main: put 8
main: put 9...
main: put 9
main: closing channel...
main: closed channel
main: waiting for worker threads to exit
main: workers exited
main: put 999...
main: put 999 - channel closed
main: closing channel...
main: closed channel
main: closing channel...
main: closed channel
outputs (a) = [1, 4, 9, 16, 25, 36, 49, 64, 81]
outputs (b) = []