util/prompt: make yes/no prompt reusable

Updates #19445

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

util/prompt/prompt.go

@@ -0,0 +1,24 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package prompt provides a simple way to prompt the user for input.
+package prompt
+
+import (
+	"fmt"
+	"strings"
+)
+
+// YesNo takes a question and prompts the user to answer the
+// question with a yes or no. It appends a [y/n] to the message.
+func YesNo(msg string) bool {
+	fmt.Print(msg + " [y/n] ")
+	var resp string
+	fmt.Scanln(&resp)
+	resp = strings.ToLower(resp)
+	switch resp {
+	case "y", "yes", "sure":
+		return true
+	}
+	return false
+}