Bug when exiting game (related to music implementation)

[FelipeMoleiro]

Describe the bug

Displaying errors upon exit of game.

Steps to Reproduce

Steps to reproduce the behavior:

1. Start the game
2. Quit it.

Message that appears:

System does not recognize call "system("killall mpg123")"
32 17.4M 32 5874k 0 0 46131 0 0:06:37 0:02:10 0:04:27 46131
curl: (23) Failure writing output to destination

Additional context

OS: Arch Linux

This is all related to the implementation of the music, which is pretty messy in my opinion. Using curl instead of sending the music to the data folder, and playing the song using system calls. Besides if we want to implement sound effects and other stuff this approach will become unbearable. I have a discussion open about this topic, but my sugestion was using SDL.

[lucasvianav]

Also, I don't think it's good to call killall by program name. We should only kill the process we started, not all of the instances of mpg123 running in the system.