fix: terminate process once it completes all the work

[alessandromazza98]

With this PR, replayor gracefully shutdown once it completes all the work.

Previously the process never terminates until you hit ctrl + c. I found it better to terminate the process once it's done working instead of leaving the process running but doing nothing.

NOTE: not a super expert in Go, this works btw.

@danyalprout

[danyalprout]

Appreciate it, thank you 🙏