set GOTOOLCHAIN min version when init go.work

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.

.github/workflows/build-operator-dont-publish.yaml

@@ -14,7 +14,7 @@ jobs:
     - name: Install Go
       uses: actions/setup-go@v2
       with:
-        go-version: 1.20.x
+        go-version: 1.21.x
 
     - name: Checkout nova-operator repository
       uses: actions/checkout@v3

Makefile

@@ -68,6 +68,8 @@ endif
 SHELL = /usr/bin/env bash -o pipefail
 .SHELLFLAGS = -ec
 
+GOTOOLCHAIN_VERSION ?= go1.21.0
+
 .PHONY: all
 all: build
 
@@ -356,7 +358,7 @@ operator-lint: $(LOCALBIN) gowork ## Runs operator-lint
 
 .PHONY: gowork
 gowork: ## Generate go.work file
-	test -f go.work || go work init
+	test -f go.work || GOTOOLCHAIN=$(GOTOOLCHAIN_VERSION) go work init
 	go work use .
 	go work use ./api
 	go work sync