Add Go script to update Go version (elastic#14201)

* Add Go script to update Go version
* Add license header
* Make file array global for easier maintenance
* Keep files on separate files for future edits.

dev-tools/cmd/update_go/update_go_version.go

@@ -0,0 +1,73 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
+var files = []string{
+	".go-version",
+	"auditbeat/Dockerfile",
+	"filebeat/Dockerfile",
+	"heartbeat/Dockerfile",
+	"journalbeat/Dockerfile",
+	"libbeat/docs/version.asciidoc",
+	"metricbeat/Dockerfile",
+	"x-pack/functionbeat/Dockerfile",
+}
+
+func main() {
+	currVersion := getGoVersion()
+	newVersion := flag.String("newversion", currVersion, "new version of Go")
+
+	flag.Parse()
+	if flag.NFlag() == 0 {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	updateGoVersion(currVersion, *newVersion)
+}
+
+func getGoVersion() string {
+	version, err := ioutil.ReadFile(".go-version")
+	checkErr(err)
+	return strings.TrimRight(string(version), "\r\n")
+}
+
+func checkErr(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func updateGoVersion(oldVersion, newVersion string) {
+	for _, file := range files {
+		fmt.Printf("Updating Go version from %s to %s in %s\n", oldVersion, newVersion, file)
+		content, err := ioutil.ReadFile(file)
+		checkErr(err)
+		updatedContent := strings.ReplaceAll(string(content), oldVersion, newVersion)
+		err = ioutil.WriteFile(file, []byte(updatedContent), 0644)
+		checkErr(err)
+	}
+}