internal/poll: handle SetDeadline to time.Now() in Plan 9
The implementation of SetDeadline in Plan 9 begins by calculating
d = the offset of the requested deadline from time.Now(). If d > 0,
a timer is set to interrupt future I/O. If d < 0, the channel is
flagged to prevent future I/O and any current I/O is cancelled.
But if d = 0, nothing happens and the deadline isn't set.
The d = 0 case should be handled the same as d < 0.
Fixes #60282
Fixes #52896
Change-Id: Id8167db3604db1c129d99376fa78a3da75417d20
Reviewed-on: https://go-review.googlesource.com/c/go/+/496137 Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com> Reviewed-by: David du Colombier <0intro@gmail.com>
Auto-Submit: Bryan Mills <bcmills@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>