set GOTOOLCHAIN min version when init go.work

In the service operators, when the golang version does not match
the version used inside the build container, dowloading the
modules can fail with:

~~~
go: go.work requires go >= 1.21.13 (running go 1.21.11; GOTOOLCHAIN=local)
~~~

This PR makes set the GOTOOLCHAIN to set 1.21.0 as the min required
version and sets it in go.work file.

Signed-off-by: Martin Schuppert <mschuppert@redhat.com>

Author: stuggi

Makefile

@@ -19,6 +19,7 @@ GINKGO ?= $(LOCALBIN)/ginkgo
 
 ## Tool Versions
 CONTROLLER_TOOLS_VERSION ?= v0.11.1
+GOTOOLCHAIN_VERSION ?= go1.21.0
 
 # ENVTEST_K8S_VERSION refers to the version of kubebuilder assets to be downloaded by envtest binary.
 ENVTEST_K8S_VERSION = 1.29
@@ -133,7 +134,7 @@ golint: get-ci-tools ## Run go lint via ci-tools script against code
 
 .PHONY: gowork
 gowork: ## Initiate go work
-	test -f go.work || go work init
+	test -f go.work || GOTOOLCHAIN=$(GOTOOLCHAIN_VERSION) go work init
 	go work use -r modules
 	go work sync