cmd/go: describe stuck ops when terminated by signal

[ccahoon]

What version of Go are you using (go version)?

go version go1.11 darwin/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOCACHE="/Users/ccahoon/Library/Caches/go-build"
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"

What did you do?

Note: I am building with GO111MODULE=on, from within my GOPATH.

1. I am building a command that imports a module defined as: module github.com/Figure53/figure53.com
2. Within that module, I import a package at github.com/Figure53/figure53.com/backend/remote, and it builds without issues.
3. I created a new file within a pre-existing package, and copy and pasted that import path. Somewhere along the way, I introduced a typo into the import path. The domain name in the import path was misspelled as gitdub.com.
4. I ran go build with GO111MODULE=on, and it hung silently until I cancelled it. I tried again a few times and got confused. It didn't seem to be CPU issue and I haven't experienced a feedback-less slow build for a while. After I stashed my changes, it built fine.
5. I read my diff, discovered my typo, fixed it, and the build worked again.

What did you expect to see?

I expected some indicator that go build was hung on trying to fetch a module, after shorter period of time. I also thought some sort of shorter timeout might make sense.

What did you see instead?

go build hung indefinitely.

Once I ran go build -v [...], I could see what it was working on, and the build hung indefinitely at:

Fetching https://gitdub.com/Figure53/figure53.com/backend/remote?go-get=1

It also is not a problem when the request returns quickly (as in an experiment I did to try to understand the problem where I changed the domain to one I control which will 404 quickly):

build github.com/Figure53/figure53.com/backend/act: cannot find module for path figure53.com/Figure53/figure53.com/backend/remote

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I am loving this module system, by the way. It's gone very smoothly for the most part. Thanks for all the great work!

[bcmills]

gitdub.com is a parked domain, and appears to hang indefinitely for HTTPS requests. We probably can't fix the hang, because we can't distinguish between a slow server and an invalid one, but we can at least do something to clarify which operation is hung.