if invoked from an instance that is not an Actor the sender will be deadLetters actor reference by default.
在akka中使用ask模式可设置超时时间，因为ask模式需等待对方的回应
implicit val timeout = Timeout(2 seconds)
(userAggregateManager ? GetUser(user)).map( _ match {
case u: User if pass.isBcrypted(u.pass) => Some(u)
case _ => None
})
