Take a look at Intel thread building blocks. https://www.threadingbuildingblocks.org/tutorial-intel-tbb-t...

Also there is Microsoft REST SDK which includes task based programming. https://casablanca.codeplex.com/wikipage?title=Programming%2...

Also there is async++ https://github.com/Amanieu/asyncplusplus/blob/master/README.... which is an implementation of the proposed c++ concurrency TS.

In January 2016 the concurrency TS was accepted so we should start seeing implementations from the compiler vendors. https://gist.github.com/StephanTLavavej/996c41f7d3732c968ede