兼容一些老项目

librf/src/sleep.h

 	template<class _Rep, class _Period>
 	inline future_t<> sleep_for(std::chrono::duration<_Rep, _Period> dt_)
 	{
-		co_await sleep_for_(std::chrono::duration_cast<std::chrono::system_clock::duration>(dt_), *current_scheduler());
+		scheduler_t* sch = current_scheduler();
+		co_await sleep_for_(std::chrono::duration_cast<std::chrono::system_clock::duration>(dt_), *sch);
 	}
 	template<class _Clock, class _Duration>
 	inline future_t<> sleep_until(std::chrono::time_point<_Clock, _Duration> tp_)
 	{
-		co_await sleep_until_(std::chrono::time_point_cast<std::chrono::system_clock::duration>(tp_), *current_scheduler());
+		scheduler_t* sch = current_scheduler();
+		co_await sleep_until_(std::chrono::time_point_cast<std::chrono::system_clock::duration>(tp_), *sch);
 	}
 
 	template <class Rep, class Period>
 	inline future_t<> operator co_await(std::chrono::duration<Rep, Period> dt_)
 	{
-		co_await sleep_for(dt_, *current_scheduler());
+		scheduler_t* sch = current_scheduler();
+		co_await sleep_for(dt_, *sch);
 	}
 
 }

librf/src/when_v2.h

 	auto when_all(_Awaitable&&... awaitor)
 		-> future_t<std::tuple<detail::awaitor_result_t<_Awaitable>...>>
 	{
-		co_return co_await when_all(*current_scheduler(), std::forward<_Awaitable>(awaitor)...);
+		scheduler_t* sch = current_scheduler();
+		co_return co_await when_all(*sch, std::forward<_Awaitable>(awaitor)...);
 	}
 
 	template<_WhenIterT _Iter
 	auto when_all(_Iter begin, _Iter end)
 		-> future_t<std::vector<detail::awaitor_result_t<decltype(*begin)>>>
 	{
-		co_return co_await when_all(*current_scheduler(), begin, end);
+		scheduler_t* sch = current_scheduler();
+		co_return co_await when_all(*sch, begin, end);
 	}
 
 	template<_ContainerT _Cont
 	auto when_any(_Awaitable&&... awaitor) 
 		-> future_t<when_any_pair>
 	{
-		co_return co_await when_any(*current_scheduler(), std::forward<_Awaitable>(awaitor)...);
+		scheduler_t* sch = current_scheduler();
+		co_return co_await when_any(*sch, std::forward<_Awaitable>(awaitor)...);
 	}
 
 	template<_WhenIterT _Iter
 	auto when_any(_Iter begin, _Iter end) 
 		-> future_t<when_any_pair>
 	{
-		co_return co_await when_any(*current_scheduler(), begin, end);
+		scheduler_t* sch = current_scheduler();
+		co_return co_await when_any(*sch, begin, end);
 	}
 
 	template<_ContainerT _Cont