set go's mod cache env var to a directory we can write to

Author: zerbitx

.github/workflows/e2e-tests.yaml

@@ -54,9 +54,11 @@ jobs:
       uses: actions/setup-go@v5
       with:
         go-version: "1.22"
-
+        
     - name: Build devspacehelper
       run: |
+        export GOMODCACHE="${{ github.workspace }}/.gomodcache"
+        mkdir -p "$GOMODCACHE"
         mkdir -p ~/.devspace/devspacehelper/latest
         CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags "-extldflags=-static" -o ~/.devspace/devspacehelper/latest/devspacehelper helper/main.go
         chmod +x ~/.devspace/devspacehelper/latest/devspacehelper