If GOPROXY is "", we set it to the default value,
"https://proxy.golang.org,direct". However, if GOPROXY is a non-empty
string that doesn't contain any URLs or keywords, we treat it as
either "off" or "noproxy", which can lead to some strange errors.
This change reports an error for this kind of GOPROXY value.
For #39180
Change-Id: If2e6e39d6f74c708e5ec8f90e9d4880e0e91894f
Reviewed-on: https://go-review.googlesource.com/c/go/+/234857
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Bryan C. Mills <bcmills@google.com> Reviewed-by: Michael Matloob <matloob@golang.org>