以下是我嘗試發送的帶有附件的代碼。    msg := &mail.Message{                    Sender: "[email protected]",                    To:     []string{addr},          Attachments : []Attachment{                           Name :"file name",                            Data :[]byte,                        ContentID :"fileid",                      },                    Subject: "Welcome to Simplyst Health: Verify your account",    if err := mail.Send(context, msg); err != nil {                    log.Errorf(ctx, "Alas, my user, the email failed to sendeth: err)                }當我嘗試保存代碼時，將引發錯誤。錯誤：cannot use []Attachment literal (type []Attachment) as type []"google.golang.org/appengine/mail".Attachment in field value