windows/svc: add new package to help create and manage Windows services

Change-Id: I58bb446aaa387b31d8a9ff4217793a170b96a7e2
Reviewed-on: https://go-review.googlesource.com/9104
Reviewed-by: Rob Pike <r@golang.org>

windows/svc/example/manage.go

@@ -0,0 +1,62 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"golang.org/x/sys/windows/svc"
+	"golang.org/x/sys/windows/svc/mgr"
+)
+
+func startService(name string) error {
+	m, err := mgr.Connect()
+	if err != nil {
+		return err
+	}
+	defer m.Disconnect()
+	s, err := m.OpenService(name)
+	if err != nil {
+		return fmt.Errorf("could not access service: %v", err)
+	}
+	defer s.Close()
+	err = s.Start("is", "manual-started")
+	if err != nil {
+		return fmt.Errorf("could not start service: %v", err)
+	}
+	return nil
+}
+
+func controlService(name string, c svc.Cmd, to svc.State) error {
+	m, err := mgr.Connect()
+	if err != nil {
+		return err
+	}
+	defer m.Disconnect()
+	s, err := m.OpenService(name)
+	if err != nil {
+		return fmt.Errorf("could not access service: %v", err)
+	}
+	defer s.Close()
+	status, err := s.Control(c)
+	if err != nil {
+		return fmt.Errorf("could not send control=%d: %v", c, err)
+	}
+	timeout := time.Now().Add(10 * time.Second)
+	for status.State != to {
+		if timeout.Before(time.Now()) {
+			return fmt.Errorf("timeout waiting for service to go to state=%d", to)
+		}
+		time.Sleep(300 * time.Millisecond)
+		status, err = s.Query()
+		if err != nil {
+			return fmt.Errorf("could not retrieve service status: %v", err)
+		}
+	}
+	return nil
+}