cmd/go: mod init outside of GOPATH silently fails
Running `go mod init` outside of GOPATH with `GO111MODULE=off`
silently fails. This behavior was undocumented.
This CL makes go mod fail with the error:
go: modules disabled by GO111MODULE=off; see 'go help modules'
Comparing with already erroring GO111MODULE=<value> conditions:
* With GO111MODULE=auto, inside GOPATH:
go modules disabled inside GOPATH/src by GO111MODULE=auto; see 'go help modules'
* With GO111MODULE=auto outside of GOPATH:
go: cannot determine module path for source directory /path/to/dir (outside GOPATH, no import comments)
Fixes #31342
Change-Id: I749787d2a8640913c4ac263072d051314d76e778
GitHub-Last-Rev:
b38447457d8cabed367ea4872cf7f238a49539c7
GitHub-Pull-Request: golang/go#31255
Reviewed-on: https://go-review.googlesource.com/c/go/+/170697
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>