go的一个接口小程序：

package mainimport (	"fmt")type IServer interface {	Start()	Stop()}type IRestartAble interface {	restart()}type ServerA struct {}type ServerB struct {}func (s *ServerA) Start() {	fmt.Println("start A")}func (s *ServerA) Stop() {	fmt.Println("stop A")}func (s *ServerA) restart() {	fmt.Println("restart A")}func (s *ServerB) Start() {	fmt.Println("start B")}func (s *ServerB) Stop() {	fmt.Println("stop B")}func main() {	sa := new(ServerA)	sb := new(ServerB)	var isa IServer = sa	isa.Start()	isa.Stop()	var irsa IRestartAble = sa	irsa.restart()	var isb IServer = sb	isb.Start()	isb.Stop()	irsb, ok := isb.(IRestartAble)	if ok {		irsb.restart()	} else {		fmt.Println("sb can't restart.")	}}