net/http: make Request.WithContext documentation less prescriptive
WithContext makes a shallow copy of a Request, and Clone makes a
deep copy. Both set the context of the new request. The distinction
between the two is clear, and it doesn't seem useful or necessary
to say that "it's rare to need WithContext".
Also update a couple locations that mention WithContext to mention
Clone as well.
Fixes #53413.
Change-Id: I89e6ddebd7d5ca6573e522fe48cd7f50cc645cdd
Reviewed-on: https://go-review.googlesource.com/c/go/+/412778 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Damien Neil <dneil@google.com>