Judging from the sources no child process seems to get killed if VS code exits - this is especially annoying if rls hangs on a laptop eating up battery unnoticed (e.g. #186 and friends). I guess one way to fix this would be by adding an exit handler like this:

process.on('exit', function() {
    child.kill();
});

The question is if you want to do this for all child processes or at all.