enum AsyncStream.Continuation.Termination A type that indicates how the stream terminated.
Discussion 解説
If an on callback is set, using task cancellation to terminate iteration of an Async results in a call to this callback.
Canceling an active iteration invokes the on callback first, then resumes by yielding nil. This means that you can perform needed cleanup in the cancellation handler. After reaching a terminal state as a result of cancellation, the Async sets the callback to nil.