chore: allow tools to be installed with newer versions of go

Author: ChristopherFry

examples/guestbook-operator/Makefile

@@ -87,25 +87,31 @@ deploy: manifests kustomize ## Deploy controller to the K8s cluster specified in
 undeploy: ## Undeploy controller from the K8s cluster specified in ~/.kube/config.
 	$(KUSTOMIZE) build config/default | kubectl delete -f -
 
-
-CONTROLLER_GEN = $(shell pwd)/bin/controller-gen
-controller-gen: ## Download controller-gen locally if necessary.
-	$(call go-get-tool,$(CONTROLLER_GEN),sigs.k8s.io/controller-tools/cmd/controller-gen@v0.4.1)
-
-KUSTOMIZE = $(shell pwd)/bin/kustomize
-kustomize: ## Download kustomize locally if necessary.
-	$(call go-get-tool,$(KUSTOMIZE),sigs.k8s.io/kustomize/kustomize/v3@v3.8.7)
-
-# go-get-tool will 'go get' any package $2 and install it to $1.
-PROJECT_DIR := $(shell dirname $(abspath $(lastword $(MAKEFILE_LIST))))
-define go-get-tool
-@[ -f $(1) ] || { \
-set -e ;\
-TMP_DIR=$$(mktemp -d) ;\
-cd $$TMP_DIR ;\
-go mod init tmp ;\
-echo "Downloading $(2)" ;\
-GOBIN=$(PROJECT_DIR)/bin go get $(2) ;\
-rm -rf $$TMP_DIR ;\
-}
-endef
+## Location to install dependencies to
+LOCALBIN ?= $(shell pwd)/bin
+$(LOCALBIN):
+	mkdir -p $(LOCALBIN)
+
+## Tool Binaries
+KUSTOMIZE ?= $(LOCALBIN)/kustomize
+CONTROLLER_GEN ?= $(LOCALBIN)/controller-gen
+
+## Tool Versions
+KUSTOMIZE_VERSION ?= v3.8.7
+CONTROLLER_TOOLS_VERSION ?= v0.4.1
+
+KUSTOMIZE_INSTALL_SCRIPT ?= "https://raw.githubusercontent.com/kubernetes-sigs/kustomize/master/hack/install_kustomize.sh"
+.PHONY: kustomize
+kustomize: $(KUSTOMIZE) ## Download kustomize locally if necessary. If wrong version is installed, it will be removed before downloading.
+$(KUSTOMIZE): $(LOCALBIN)
+	@if test -x $(LOCALBIN)/kustomize && ! $(LOCALBIN)/kustomize version | grep -q $(KUSTOMIZE_VERSION); then \
+			echo "$(LOCALBIN)/kustomize version is not expected $(KUSTOMIZE_VERSION). Removing it before installing."; \
+			rm -rf $(LOCALBIN)/kustomize; \
+	fi
+	test -s $(LOCALBIN)/kustomize || { curl -Ss $(KUSTOMIZE_INSTALL_SCRIPT) --output install_kustomize.sh && bash install_kustomize.sh $(subst v,,$(KUSTOMIZE_VERSION)) $(LOCALBIN); rm install_kustomize.sh; }
+
+.PHONY: controller-gen
+controller-gen: $(CONTROLLER_GEN) ## Download controller-gen locally if necessary. If wrong version is installed, it will be overwritten.
+$(CONTROLLER_GEN): $(LOCALBIN)
+	test -s $(LOCALBIN)/controller-gen && $(LOCALBIN)/controller-gen --version | grep -q $(CONTROLLER_TOOLS_VERSION) || \
+	GOBIN=$(LOCALBIN) go install sigs.k8s.io/controller-tools/cmd/controller-gen@$(CONTROLLER_TOOLS_VERSION)