Merge pull request #21943 from kubernetes/copilot/fix-golang-1-25-build

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

Author: medyagh

.gitignore

@@ -5,6 +5,7 @@
 
 # Folders
 .cache
+.modcache
 _obj
 _test
 

Makefile

@@ -184,7 +184,7 @@ endef
 
 # $(call DOCKER, image, command)
 define DOCKER
-	docker run --rm -e GOCACHE=/app/.cache -e IN_DOCKER=1 --user $(shell id -u):$(shell id -g) -w /app -v $(PWD):/app:Z -v $(GOPATH):/go:Z --init $(1) /bin/bash -c '$(2)'
+	docker run --rm -e GOCACHE=/app/.cache -e GOPATH=/go -e GOMODCACHE=/app/.modcache -e IN_DOCKER=1 --user $(shell id -u):$(shell id -g) -w /app -v $(PWD):/app:Z -v $(GOPATH):/go:Z --init $(1) /bin/bash -c '$(2)'
 endef
 
 ifeq ($(BUILD_IN_DOCKER),y)