Implements a task local storage variable.
struct TaskLocal(T) ;
Task local variables, similar to thread local variables, exist separately in each task. Consequently, they do not need any form of synchronization when accessing them.
Note, however, that each TaskLocal variable will increase the memory footprint of any task that uses task local storage. There is also an overhead to access TaskLocal variables, higher than for thread local variables, but generelly still O(1) (since actual storage acquisition is done lazily the first access can require a memory allocation with unknown computational costs).
FiberLocal instances MUST be declared as static/global thread-local variables. Defining them as a temporary/stack variable will cause crashes or data corruption!