CI: Fix Go 1.25 build failure in kube-cross Docker by setting GOPATH and GOMODCACHE

[Copilot]

Go 1.25 changed default behavior when GOPATH is unset—it now defaults to GOROOT, causing build failures in the kube-cross Docker container with permission errors writing to /usr/local/go/pkg/mod.

Changes

• Makefile: Explicitly set GOPATH=/go and GOMODCACHE=/app/.modcache in DOCKER function
• .gitignore: Add .modcache to ignore module cache directory

Context

The Makefile's DOCKER function mounts the host's GOPATH to /go but didn't set the environment variable. In Go 1.25, this causes:

warning: both GOPATH and GOROOT are the same directory (/usr/local/go)
go: writing go.mod cache: mkdir /usr/local/go/pkg/mod/cache/download: permission denied

Setting GOMODCACHE to a writable location in /app (project directory) ensures module downloads work regardless of GOPATH mount permissions.

Fixes builds with MINIKUBE_BUILD_IN_DOCKER=y on Jenkins and Functional_Verified workflow.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• registry.k8s.io
  • Triggering command: /usr/bin/docker docker run --rm registry.k8s.io/build-image/kube-cross:v1.34.0-go1.24.6-bullseye.0 /bin/bash -c echo "GOROOT: $GOROOT"; echo "GOPATH: $GOPATH"; go env GOROOT; go env GOPATH (dns block)

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>bumping golang 1.25 failure when building using "kube-cross image"</issue_title>
<issue_description>When trying to bump the golang from 1.24 to 1.25 I the build fails in jenkins when it is built in Docker using the Kube Cross image (this is after I removed hyperkit which is can not be built with 1.25) but now got a new blocker

# NOTE: "latest" as of 2021-02-06. kube-cross images aren't updated as often as Kubernetes
# https://github.com/kubernetes/kubernetes/blob/master/build/build-image/cross/VERSION

# BUILD_IMAGE 	?= registry.k8s.io/build-image/kube-cross:$(GO_K8S_VERSION_PREFIX)-go$(GO_VERSION)-bullseye.0

I noticed build fails in Jenkins (which runs in docker) "MINIKUBE_BUILD_IN_DOCKER" and also Functiona_Verified job also fails (builds minikube in docker) but "Functional" workflow passes (builds it on Ubuntu Baremetal

Functional_Verified Workflow Build (builds in Docker

minikube/.github/workflows/functional_verified.yml

Line 47 in bac7021

MINIKUBE_BUILD_IN_DOCKER=y make e2e-linux-arm64

MINIKUBE_BUILD_IN_DOCKER=y make e2e-linux-arm64

Functional Normal build passee

minikube/.github/workflows/functional_test.yml

Line 46 in bac7021

make e2e-linux-amd64 e2e-darwin-amd64

We need to find out why new KubeCorss Image fails and how to fix it, because on Jenkins we should not rely on building on host

Logs From Jenkins build (trimmed)

12:35:43 Unable to find image 'registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0' locally
12:35:43 v1.35.0-go1.25.3-bullseye.0: Pulling from build-image/kube-cross
12:35:43 3adbbc83e99d: Waiting
12:37:12 a949bcef8c2a: Pull complete
12:37:12 Digest: sha256:2d42755343ada0f56e9d381916edf5d2dbd00050643d4f558b9bcd891d3bdc81
12:37:12 Status: Downloaded newer image for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:12 Status: Image is up to date for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:12 Status: Downloaded newer image for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:12 Status: Image is up to date for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:12 Digest: sha256:2d42755343ada0f56e9d381916edf5d2dbd00050643d4f558b9bcd891d3bdc81
12:37:12 Status: Image is up to date for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:12 Digest: sha256:2d42755343ada0f56e9d381916edf5d2dbd00050643d4f558b9bcd891d3bdc81
12:37:12 Status: Image is up to date for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:12 Digest: sha256:2d42755343ada0f56e9d381916edf5d2dbd00050643d4f558b9bcd891d3bdc81
12:37:12 Status: Image is up to date for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:12 Digest: sha256:2d42755343ada0f56e9d381916edf5d2dbd00050643d4f558b9bcd891d3bdc81
12:37:12 Status: Image is up to date for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:13 Digest: sha256:2d42755343ada0f56e9d381916edf5d2dbd00050643d4f558b9bcd891d3bdc81
12:37:13 Status: Image is up to date for registry.k8s.io/build-image/kube-cross:v1.35.0-go1.25.3-bullseye.0
12:37:13 warning: both GOPATH and GOROOT are the same directory (/usr/local/go); see https://go.dev/wiki/InstallTroubleshooting
12:37:13 warning: both GOPATH and GOROOT are the same directory (/usr/local/go); see https://go.dev/wiki/InstallTroubleshooting
12:37:13 warning: both GOPATH and GOROOT are the same directory (/usr/local/go); see https://go.dev/wiki/InstallTroubleshooting
# Get Repeated hunddreds of times...

12:37:13 GOOS="linux" GOARCH="s390x"  \
12:37:13 go build -tags "libvirt_dlopen" -ldflags="-X k8s.io/minikube/pkg/version.version=v1.37.0 -X k8s.io/minikube/pkg/version.isoVersion=v1.37.0-1763503576-21924 -X k8s.io/minikube/pkg/version.gitCommitID="2d19d546682a9aac70700f5e2d85cb8e7ae0d67a" -X k8s.io/minikube/pkg/version.storageProvisionerVersion=v5" -a -o out/minikube-linux-s390x k8s.io/minikube/cmd/minikube

12:37:13 GOOS="windows" GOARCH="amd64"  \
12:37:13 go build -tags "libvirt_dlopen" -ldflags="-X k8s.io/minikube/pkg/version.version=v1.37.0 -X k8s.io/minikube/pkg/version.isoVersion=v1.37.0-1763503576-21924 -X k8s.io/minikube/pkg/version.gitCommitID="2d19d546682a9aac70700f5e2d85cb8e7ae0d67a" -X k8s.io/minikube/pkg/version.storageProvisionerVersion=v5" -a -o out/minikube-windows-amd64 k8s.io/minikube/cmd/minikube
12:37:13 warning: both GOPATH and GOROOT are the same directory (/usr/local/go); see https://go.dev/wiki/InstallTroubleshooting
# ...

12:37:13 go: downloading gopkg.in/yaml.v2 v2.4.0
12:37:13 go: downloading golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c
12:37:13 warning: both GOPATH and GOROOT are the same directory (/usr/local/go); see https://go.dev/wiki/InstallTroubleshooting
12:37:13 GOOS="linux" GOARCH="386"  \
12:37:13 go build -tags "libvirt_dlopen" -ldflags="-X k8...

</details>

- Fixes kubernetes/minikube#21942

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[k8s-ci-robot]

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Can one of the admins verify this patch?

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Copilot, medyagh

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/ok-to-test

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@Copilot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
integration-kvm-containerd-linux-x86-64	f8e5c88	link	true	/test integration-kvm-containerd-linux-x86-64
integration-kvm-crio-linux-x86-64	f8e5c88	link	true	/test integration-kvm-crio-linux-x86-64
integration-docker-containerd-linux-x86-64	f8e5c88	link	true	/test integration-docker-containerd-linux-x86-64
integration-docker-crio-linux-x86-64	f8e5c88	link	true	/test integration-docker-crio-linux-x86-64
integration-none-docker-linux-x86-64	f8e5c88	link	true	/test integration-none-docker-linux-x86-64
integration-docker-docker-linux-x86-64	f8e5c88	link	true	/test integration-docker-docker-linux-x86-64

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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