cmd/go: modules eagerly downloaded even with populated cache

[frioux]

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

$ go version
go version go1.14beta1 linux/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/frew/.cache/go-build"
GOENV="/home/frew/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/frew/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org"
GOROOT="/home/frew/sdk/go1.14beta1"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/frew/sdk/go1.14beta1/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/frew/code/zr0/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/run/shm/go-build397670914=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Turned off my network and ran go test ./...

What did you expect to see?

My tests run.

What did you see instead?

Blocking and searching for modules:

$ go test ./...                                                                                
go: finding versions for github.com                                                            
go: finding versions for github.com/pierrec/lz4                        
go: finding versions for github.com/pierrec/lz4/internal                                       
go: finding versions for github.com/pierrec                                                    
go: finding versions for github.com/pierrec/lz4/internal/xxh32                 
^C

This is weird. It doesn't reproduce every time, but I notice it a lot more now while I'm outside of Los Angeles, visiting family in TX where the internet is worse. To be clear: I already have a populated go module cache, so I should only need to download modules when I update my go.mod, which is pretty rare. I don't think this is new with 1.14, I just think it's related to the worse internet over the holidays.

[bcmills]

What happens if you let go test ./... keep running? (Do you get an error?)
Does the command succeed with the network on?

At first blush, this looks like an instance of #26152.

[frioux]

It's pretty hard to reproduce this without flaky internet (just turning the wifi off doesn't surface the issue.) I'll keep an eye out for if it shows up in the meantime, I guess?