Class instance variables scope clarification

While going through the 'Dodge the creeps!' tutorial in C++, I noticed that signals' callbacks don't seem to observe changes made to a class instance variable:

[Hud::is_game_over](https://github.com/m4gr3d/godot_dodge_the_creeps/blob/170d2e38a314ab4d343dac8ec2b627a3575c6e2e/src/hud.h#L24) is updated in [Hud::show_game_over](https://github.com/m4gr3d/godot_dodge_the_creeps/blob/170d2e38a314ab4d343dac8ec2b627a3575c6e2e/src/hud.cpp#L36), yet when the [Hud::on_MessageTimer_timeout](https://github.com/m4gr3d/godot_dodge_the_creeps/blob/170d2e38a314ab4d343dac8ec2b627a3575c6e2e/src/hud.cpp#L53) callback is fired, the updated value of [Hud::is_game_over](https://github.com/m4gr3d/godot_dodge_the_creeps/blob/170d2e38a314ab4d343dac8ec2b627a3575c6e2e/src/hud.h#L24) is not reflected.

I validated that the callback is happening to the same object and on the same thread as when the instance variable is updated.

This is probably not a bug, and most likely just some clarifications are needed to explain why that behavior is observed (if that's the expected behavior).