From 2977a4b1cbebd851355538b8997c161a1db8651f Mon Sep 17 00:00:00 2001
From: Predrag Rogic <prezha@users.noreply.github.com>
Date: Fri, 16 Oct 2020 23:06:28 +0100
Subject: [PATCH 1/2] get greatest instead of just latest version

---
 go.mod                                        |  1 +
 .../update_kubernetes_version.go              | 28 ++++++++-----------
 2 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/go.mod b/go.mod
index b9919572fe..550dd39329 100644
--- a/go.mod
+++ b/go.mod
@@ -73,6 +73,7 @@ require (
 	golang.org/x/build v0.0.0-20190927031335-2835ba2e683f
 	golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37
 	golang.org/x/exp v0.0.0-20200224162631-6cc2880d07d6
+	golang.org/x/mod v0.3.0
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d
 	golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a
 	golang.org/x/sys v0.0.0-20200523222454-059865788121
diff --git a/hack/kubernetes_version/update_kubernetes_version.go b/hack/kubernetes_version/update_kubernetes_version.go
index 146506e9b4..50af8e6c81 100644
--- a/hack/kubernetes_version/update_kubernetes_version.go
+++ b/hack/kubernetes_version/update_kubernetes_version.go
@@ -40,6 +40,7 @@ import (
 	"text/template"
 	"time"
 
+	"golang.org/x/mod/semver"
 	"golang.org/x/oauth2"
 
 	"github.com/google/go-github/v32/github"
@@ -399,26 +400,19 @@ func ghReleases(ctx context.Context, owner, repo, token string) (stable, latest
 		}
 		for _, rl := range rls {
 			ver := rl.GetName()
-			if ver == "" {
+			if !semver.IsValid(ver) {
 				continue
 			}
-			// check if ver version is a release (ie, 'v1.19.2') or a
-			// pre-release (ie, 'v1.19.3-rc.0' or 'v1.19.0-beta.2') channel ch
-			// note: github.RepositoryRelease GetPrerelease() bool would be useful for all pre-rels
-			ch := strings.Split(ver, "-")
-			if len(ch) == 1 && stable == "" {
-				stable = ver
-			} else if len(ch) > 1 && latest == "" {
-				if strings.HasPrefix(ch[1], "rc") || strings.HasPrefix(ch[1], "beta") {
-					latest = ver
-				}
+			// check if ver version is release (ie, 'v1.19.2') or pre-release (ie, 'v1.19.3-rc.0' or 'v1.19.0-beta.2')
+			prerls := semver.Prerelease(ver)
+			if prerls == "" {
+				stable = semver.Max(ver, stable)
+			} else if strings.HasPrefix(prerls, "-rc") || strings.HasPrefix(prerls, "-beta") {
+				latest = semver.Max(ver, latest)
 			}
-			if stable != "" && latest != "" {
-				// make sure that v.Latest >= stable
-				if latest < stable {
-					latest = stable
-				}
-				return stable, latest, nil
+			// make sure that latest >= stable
+			if semver.Compare(latest, stable) == -1 {
+				latest = stable
 			}
 		}
 		if resp.NextPage == 0 {

From 2c1efe857af7aec93037ad3fb4de865eba4ab61b Mon Sep 17 00:00:00 2001
From: Predrag Rogic <prezha@users.noreply.github.com>
Date: Sat, 17 Oct 2020 00:59:05 +0100
Subject: [PATCH 2/2] fix klog 'no such flag -logtostderr' with InitFlags

---
 hack/kubernetes_version/update_kubernetes_version.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hack/kubernetes_version/update_kubernetes_version.go b/hack/kubernetes_version/update_kubernetes_version.go
index 50af8e6c81..8d68b61324 100644
--- a/hack/kubernetes_version/update_kubernetes_version.go
+++ b/hack/kubernetes_version/update_kubernetes_version.go
@@ -127,9 +127,10 @@ func (p *Patch) apply(data interface{}) (changed bool, err error) {
 }
 
 func main() {
+	klog.InitFlags(nil)
 	// write log statements to stderr instead of to files
 	if err := flag.Set("logtostderr", "true"); err != nil {
-		fmt.Printf("Error setting 'logtostderr' klog flag: %v", err)
+		fmt.Printf("Error setting 'logtostderr' klog flag: %v\n", err)
 	}
 	flag.Parse()
 	defer klog.Flush()