cmd/go: confusing error message when downloading modules with no internet connection

[Russiancold]

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

$ go version
1.12.9

Does this issue reproduce with the latest release?

Yes

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

go env GOOS=linux GOARCH=amd64

$ go env

What did you do?

I've tried to build my go app with modules in docker.

FROM golang:1.12.9 as builder

ENV GO111MODULE=on
WORKDIR /app

COPY go.mod .
COPY go.sum .

RUN go mod download

COPY . .

RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o encashment


FROM scratch
COPY --from=builder /app/encashment /encashment/
EXPOSE 8080
ENTRYPOINT ["/app/encashment"]

The problem was that my docker had no internet connection and go mod download couldn't load packages. I was very confused with an error message it returns. Suddenly, I don't know exactly what was wrong and how to reproduce this properly. But I did:

pkill docker
iptables -t nat -F
ifconfig docker0 down
brctl delbr docker0
docker -d

And this worked for me.

What did you expect to see?

Error message informing that something is wrong with internet connection.

What did you see instead?

go: finding github.com/gorilla/mux v1.7.3
go: github.com/gorilla/[email protected]: unknown revision v1.7.3
go: error loading module requirements

[seankhliao]

Current error message seems reasonable.

$ go mod download
go: github.com/gorilla/[email protected]: Get "https://proxy.golang.org/github.com/gorilla/mux/@v/v1.8.0.mod": dial tcp: lookup proxy.golang.org: i/o timeout