@Fernando Branbila Cunha Junior Lol, seriously bro, I sincerely think that is the best answer. I'll elaborate....
People can correct me if I am wrong but open source projects, especially successful ones, want developers that are extremely skillful and already know what they are doing. That is needless to say. Yes, many are accommodating to new developers but that is because a project has all sorts of work that needs to be done. I.e., finding typos, documentation, testing on different environments, grunt work. They definitely don't want you to start working on the core design and functionality. Yet that is exactly what you need to work on to get good. Sure reading their code might help. What would help significantly more is coming up with something that would improve your life or work, increases your efficient is interesting and challenging.
So like I said if you are new to coroutines and want to learn and apply to real world cases go build your own project.