Errors with Ruby 3.1.2

[ghn]

Describe the problem

Lots of warnings triggered when used with ruby 3.1.2

Steps to reproduce the problem

With ruby 3.1.2

bundle exec rspec

Actual behaviour

Error:

lib/finite_machine/observer.rb:22:in block in cleanup_callback_queue': undefined local variable or method callback_queue' for FiniteMachine::Observer:Class (NameError)

Expected behaviour

Specs pass without warnings

Describe your environment

• OS version: osx 12
• Ruby version: 3.1.2
• FiniteMachine version: master

[ghn]

Related PR https://github.com/piotrmurach/finite_machine/pull/74

[dup2]

Would be nice to fix this and release, it is not usable on ruby 3.1+ otherwise