SIGSEGV: Illegal storage access. (Attempt to read from nil?) in coroutines

[mratsim]

Also every major language has abandoned fibers / green-threads / stackful 
coroutines for their standard library.

  * Go: 
<https://docs.google.com/document/d/1wAaf1rYoM4S4gtnPh0zOlGzWtrZFQ5suE8qr2sD8uWQ/pub>
  * Java in 0.1
  * Rust: 
<https://mail.mozilla.org/pipermail/rust-dev/2013-November/006314.html>