$ for i in $(seq 1 100); do ./bad.sh | grep 'got lock'; done | sort | uniq -c
    100 Process 1 got lock
    100 Process 2 got lock
    100 Process 3 got lock
$ for i in $(seq 1 100); do ./good.sh | grep 'got lock'; done | sort | uniq -c
     80 Process 1 got lock
     17 Process 2 got lock
      3 Process 3 got lock
$

$ ./example.sh & ./example.sh &
[1] 15157
[2] 15158
$ 15157 locking
15158 locking
15157  got lock, working...
15158 locking
15158 locking
15157 unlocking
15158 locking
15158  got lock, working...
15158 unlocking

[1]-  Done                    ./example.sh
[2]+  Done                    ./example.sh
$

$ ./example.sh
15202 locking
15202  got lock, working...
^C
$ ./example.sh
15205 locking
15205 locking
15205 locking
15205 locking
15205 locking
15205 failed
$