Merge pull request #296 from cybozu-go/push-mumuzkuksspl

follow Kubebuilder recommendations in maintenance

Author: satoru-takeuchi

docs/maintenance.md

@@ -21,27 +21,29 @@ To change the versions, edit the following files.
 - `README.md`
 - `versions.mk`
 
-We should also update go.mod by the following commands. Note that `k8s.io/api`, `k8s.io/apimachinery`, and `k8s.io/client-go` use `v0.x.x` tags (e.g., v1.35.4 → v0.35.4), while `k8s.io/kubernetes` uses `v1.x.x` tags directly.
+We should also update go.mod. According to [the Kubebuilder documentation](https://book.kubebuilder.io/versions_compatibility_supportability), we should use versions compatible with Kubebuilder, so refer to the samples in the latest Kubebuilder testdata directory (e.g., https://github.com/kubernetes-sigs/kubebuilder/blob/v4.1.1/testdata/project-v4/go.mod#L8-L11 and https://github.com/kubernetes-sigs/kubebuilder/blob/v4.1.1/testdata/project-v4/Makefile#L162) to see which versions should be used.
+
+First, update `k8s.io/*` libraries. Please note that `k8s.io/api`, `k8s.io/apimachinery`, and `k8s.io/client-go` use `v0.x.x` tags (e.g., v1.35.4 → v0.35.4), while `k8s.io/kubernetes` uses `v1.x.x` tags directly.
 
 ```bash
 $ VERSION=0.<minor>.<patch>  # e.g. 0.35.4 for Kubernetes 1.35.4
 $ go get k8s.io/api@v${VERSION} k8s.io/apimachinery@v${VERSION} k8s.io/client-go@v${VERSION}
 $ go get k8s.io/kubernetes@v1.<minor>.<patch>  # e.g. v1.35.4
 ```
 
-Read the [`controller-runtime`'s release note](https://github.com/kubernetes-sigs/controller-runtime/releases), and update to the newest version that is compatible with all supported kubernetes versions. If there are breaking changes, we should decide how to manage these changes.
+Next, update controller-runtime by the following command. Before updating it, please read the [`controller-runtime`'s release note](https://github.com/kubernetes-sigs/controller-runtime/releases). If there are breaking changes, we should decide how to manage these changes.
 
 ```
 $ VERSION=<upgrading controller-runtime version>
 $ go get sigs.k8s.io/controller-runtime@v${VERSION}
 ```
 
-Read the [`controller-tools`'s release note](https://github.com/kubernetes-sigs/controller-tools/releases), and update to the newest version that is compatible with all supported kubernetes versions. If there are breaking changes, we should decide how to manage these changes.
+Finally, update controller-tools. Before updating it, please read the [`controller-tools`'s release note](https://github.com/kubernetes-sigs/controller-tools/releases). If there are breaking changes, we should decide how to manage these changes.
 To change the version, edit `versions.mk`.
 
 #### Go
 
-Choose the same version of Go [used by the latest Kubernetes](https://github.com/kubernetes/kubernetes/blob/master/go.mod) supported by Mantle.
+Choose the version compatible with Kubebuilder (e.g., https://github.com/kubernetes-sigs/kubebuilder/blob/v4.1.1/testdata/project-v4/go.mod#L3).
 
 Edit the following files.
 
@@ -51,7 +53,7 @@ Edit the following files.
 
 #### Depending tools
 
-The following tools do not depend on other software, use the latest versions.
+The following tools don't depend on other software, so use the latest versions.
 To change their versions, edit `versions.mk`.
 
 - [helm](https://github.com/helm/helm/releases)

go.mod

@@ -1,8 +1,6 @@
 module github.com/cybozu-go/mantle
 
-go 1.25.0
-
-toolchain go1.25.7
+go 1.25.7
 
 require (
 	github.com/aws/aws-sdk-go-v2 v1.41.7