cmd/go: go test intermittently hangs before test binary execution on windows/amd64 #81368

Go version

go version go1.27.0 windows/amd64

Go 1.27.1 was also independently observed exhibiting the same hang (see "Go version A/B" below).

Output of go env in your module/workspace

set AR=ar
set CC=gcc
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_ENABLED=1
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set CXX=g++
set GCCGO=gccgo
set GO111MODULE=
set GOAMD64=v1
set GOARCH=amd64
set GOAUTH=netrc
set GOBIN=C:\Users\runneradmin\go\bin
set GOCACHE=C:\Users\runneradmin\AppData\Local\go-build
set GOCACHEPROG=
set GODEBUG=
set GOENV=C:\Users\runneradmin\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFIPS140=off
set GOFLAGS=
set GOGCCFLAGS=-m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\RUNNER~1\AppData\Local\Temp\go-build2098717326=/tmp/go-build -gno-record-gcc-switches
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMOD=D:\a\network-doctor\network-doctor\go.mod
set GOMODCACHE=C:\Users\runneradmin\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPACKAGESDRIVER=
set GOPATH=C:\Users\runneradmin\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\hostedtoolcache\windows\go\1.27.0\x64
set GOSUMDB=sum.golang.org
set GOTELEMETRY=local
set GOTELEMETRYDIR=C:\Users\runneradmin\AppData\Roaming\go\telemetry
set GOTMPDIR=
set GOTOOLCHAIN=local
set GOTOOLDIR=C:\hostedtoolcache\windows\go\1.27.0\x64\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.27.0
set GOWORK=
set PKG_CONFIG=pkg-config

Captured on GitHub-hosted windows-2025-vs2026 (image version 20260824.214.3, runner version 2.337.0, Windows build 10.0.26100), GOTOOLCHAIN=local, from reproducing run: https://github.com/heymaikol/network-doctor/actions/runs/33948156093 (job 101257868494).

What did you do?

Repository: https://github.com/heymaikol/network-doctor

Primary reproducer:

go test ./internal/ui

Also observed under:

go test ./...

The fresh reproducing run https://github.com/heymaikol/network-doctor/actions/runs/33948156093 ran the literal command go test ./internal/ui on Go 1.27.0 and hung until the 20-minute outer GitHub Actions timeout, producing no package test output before cancellation.

Decisive discriminators (from paired runs on the same runner):

• go build ./internal/ui completes
• go list ./internal/ui completes
• go test -c ./internal/ui -o ui.test.exe completes quickly (~2.6s)
• the compiled test binary, invoked directly from package CWD internal/ui, passes with exit code 0 in about 55s
• paired go test ./internal/ui can hang
• isolated package testing is sufficient; ./... aggregation is not required

What did you see happen?

On GitHub-hosted Windows runners, go test ./internal/ui intermittently hangs before the package test binary is observed executing and never produces its normal package-level terminal result.

For aggregate testing, go test ./... can complete every other package while internal/ui never reports completion.

Evidence localizes the failure to cmd/go's orchestration path before the test binary is observed executing.

We do not claim an exact cmd/go scheduler race is proven, a specific lock or goroutine identified, or a precise cmd/go source location known. Direct invocation does not necessarily reproduce every flag, environment variable, pipe arrangement, or other invocation detail supplied by go test.

Process observer

https://github.com/heymaikol/network-doctor/actions/runs/33927281491

During the sustained pathological interval, the top-level go.exe remained alive, accumulated CPU time increased, and no persistent compile.exe, no persistent link.exe, and no *.test.exe were observed.

Other notable runs

Fresh environment + reproducer — https://github.com/heymaikol/network-doctor/actions/runs/33948156093
Exact Windows Go 1.27.0 go version and go env captured; literal go test ./internal/ui; hangs to the 20-minute outer timeout; no package test output before cancellation.

Corrected direct-binary discriminator — https://github.com/heymaikol/network-doctor/actions/runs/33938996888
go test -c ./internal/ui -o ui.test.exe succeeds in about 2.6s; the compiled binary run from package CWD internal/ui passes the full test suite with exit code 0 in about 55s; paired go test ./internal/ui hangs to the outer timeout.

Process observer — https://github.com/heymaikol/network-doctor/actions/runs/33927281491
As described above.

Go version A/B — https://github.com/heymaikol/network-doctor/actions/runs/33934720024
Go 1.27.0 hangs; Go 1.27.1 hangs.

Isolated package vs aggregate — https://github.com/heymaikol/network-doctor/actions/runs/33936232700
go test ./internal/ui hangs; go test ./... hangs with internal/ui lacking a terminal result; multi-package aggregation is not required.

First direct-binary discriminator — https://github.com/heymaikol/network-doctor/actions/runs/33937674466
Compile succeeds; the compiled test binary is accidentally launched from a wrong/non-package CWD; it executes but fails at TestJobStatusString because jobs.go cannot be found; paired go test ./internal/ui hangs; this led to the corrected-CWD run 33938996888.

Earlier successful diagnostic run — https://github.com/heymaikol/network-doctor/actions/runs/33914012572
Diagnostic jobs completed successfully, including successful compile-only construction; this run is not a hang.

Timing perturbations

-p 1 completed in some runs; an earlier -p=1 run also hung; -x completed in some runs. These are timing/execution perturbations only. -p 1 is not a reliable workaround, and -x is not recommended as a workaround.

What did you expect to see?

go test ./internal/ui should complete and produce a normal package-level result.

go test ./... should complete and produce a result for every package.

Maintainer request

• What additional cmd/go diagnostics would be most useful during a hung process?
• Is there a supported way to capture cmd/go scheduler / action-graph state?
• What degree of minimization would be useful for a smaller reproducer?