Fix CI for 1.16

Run `go mod tidy` before building image so the go.mod has
the required deps.

See https://blog.golang.org/go116-module-changes#TOC_3.

pkg/cli/alpha/config-gen/cmd.go

@@ -24,6 +24,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	// TODO: switch to embed
 	"github.com/markbates/pkger"
 	"github.com/spf13/cobra"
 

test/e2e/utils/test_context.go

@@ -220,6 +220,14 @@ func (t *TestContext) Make(makeOptions ...string) error {
 	return err
 }
 
+// Tidy runs `go mod tidy` so that go 1.16 build doesn't fail.
+// See https://blog.golang.org/go116-module-changes#TOC_3.
+func (t *TestContext) Tidy() error {
+	cmd := exec.Command("go", "mod", "tidy")
+	_, err := t.Run(cmd)
+	return err
+}
+
 // Destroy is for cleaning up the docker images for testing
 func (t *TestContext) Destroy() {
 	//nolint:gosec

test/e2e/v3/plugin_cluster_test.go

@@ -117,6 +117,10 @@ func Run(kbc *utils.TestContext) {
 	var controllerPodName string
 	var err error
 
+	By("updating the go.mod")
+	err = kbc.Tidy()
+	ExpectWithOffset(1, err).NotTo(HaveOccurred())
+
 	By("building the controller image")
 	err = kbc.Make("docker-build", "IMG="+kbc.ImageName)
 	ExpectWithOffset(1, err).NotTo(HaveOccurred())