Fibers provides an alternative cooperative multi-tasking approach to Coroutines with less overhead. It is not a drop-in replacement but is intended for heavy usage situations.
Read the full documentation at http://www.askowl.net/unity-fibers
This source has been compiled and integrity tested using Unity 2018.3.0b1 using the .NET 4 equivalent compiler.
Open the scene "Assets/Askowl/Fibers/Introduction to Fibers" for more details and to turn integrity testing on and off.