If you have to use C/C++ use a library that has done it for you. If you don't then you can use Rust, Go or Erlang/Elixir all of which have excellent implementations.
I'll give you another example: ropes are string classes with more complex data storage, useful for optimizing mutations and cutting down copies. The concept is easy to understand, and personally I've implemented them a number of times, but didn't know about the formalized term until the last year or so.
The last sentence is a bit unfair and presumptuous, I think.
If you're not familiar with implementing schedulers and concurrent systems then beware that implementing fibers from scratch is likely to result in some subtle and hard to debug problems.
If you have to use C/C++ you may well get better results using a library. If you aren't tied to the language then Erlang/Elixir, Go and Rust all have excellent implementations that have more language support.
Its a bit messy, sure. But I don't think I have any subtle bugs and was not hard to debug. Performance is good too.
What I want to say is: it is easy to do, even I can :P
Actually for full disclosure I should say that I am currently building a telecomms system in Elixir. I find the decades of battle testing in the BEAM reassuring.