Not what I wanted to achieve, but the lexer contains some frequently used methods and is fairly simple and straight-forward, but if you want to learn the semantics why not just go to their docs? https://crystal-lang.org/docs/syntax_and_semantics/index.htm...

> Consider this use case: I spawn five fibers. Can I send the same mutable object to all five? If so, can they attempt to mutate the object without properly taking turns? (e.g., using a mutex)

Taken from the docs:

Crystal has Channels inspired by CSP[1]. They allow communicating data between fibers without sharing memory and without having to worry about locks, semaphores or other special structures.

...

Because at this moment there's only a single thread executing your code, accessing and modifying a global variable in different fibers will work just fine. However, once multiple threads (parallelism) is introduced in the language, it might break. That's why the recommended mechanism to communicate data is using channels and sending messages between them. Internally, a channel implements all the locking mechanisms to avoid data races, but from the outside you use them as communication primitives, so you (the user) don't have to use locks.

[1] - https://en.wikipedia.org/wiki/Communicating_sequential_proce...