The hours, minutes, and seconds fields for time zones
should not have any plus or minus signs.
Use getnum instead of atoi since the latter implicitly
handles leading signs, while the former does not.
Fixes #54570
Change-Id: If9600170af3af999739c27d81958e3649946913a
Reviewed-on: https://go-review.googlesource.com/c/go/+/425038 Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Joseph Tsai <joetsai@digital-static.net>
Auto-Submit: Joseph Tsai <joetsai@digital-static.net> Reviewed-by: Rob Pike <r@golang.org>