Destroys a std::experimental::shared_future object.
~shared_future();
Destroys *this.
If there is no longer a std::experimental::promise or std::experimental::packaged_task instance
associated with the asynchronous result associated with *this,
and this is the last std::experimental::shared_future instance
associated with that asynchronous result, then destroy that asynchronous
result.
Nothing
#include <experimental/future>