An abstraction over coroutine-based io poller and asynchronous task.
This design allows us to easily swap our fiber system to another one provided by the host application.
.package(url:"https://github.com/swiftstack/async.git",.branch("fiber"))async.main is just a wrapper around async.task to hide do {} catch {}
import Fiber
async.use(Fiber.self)async.main{async.task{async.sleep(until:.now)}}
loop.run()