在Akka HTTP客户端端遇到WebSocket意外关闭的情况下，可以通过以下代码示例来解决：

import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.model._
import akka.http.scaladsl.model.ws._
import akka.stream.ActorMaterializer
import akka.stream.scaladsl._

import scala.concurrent.Future

object WebSocketClientExample extends App {
  implicit val system = ActorSystem()
  implicit val materializer = ActorMaterializer()
  import system.dispatcher

  // WebSocket 消息处理器
  val webSocketHandler: Flow[Message, Message, Future[WebSocketUpgradeResponse]] = Flow.fromSinkAndSourceMat(
    Sink.foreach[Message] {
      case message: TextMessage.Strict =>
        println(s"Received message: ${message.text}")
      case message: TextMessage.Streamed =>
        message.textStream.runForeach { text =>
          println(s"Received streamed message: $text")
        }
      case _ =>
        println("Unknown message received")
    },
    Source.maybe[Message]
  )(Keep.right)

  // 创建 WebSocket 连接
  val (upgradeResponse, closed) =
    Http().singleWebSocketRequest(
      WebSocketRequest("ws://localhost:9000/ws"), // WebSocket 服务器地址
      webSocketHandler
    )

  val connected = upgradeResponse.flatMap { upgrade =>
    if (upgrade.response.status == StatusCodes.SwitchingProtocols) {
      Future.successful(())
    } else {
      Future.failed(new RuntimeException(s"WebSocket connection failed: ${upgrade.response.status}"))
    }
  }

  connected.onComplete {
    case scala.util.Success(_) =>
      println("WebSocket connected")
    case scala.util.Failure(ex) =>
      println(s"WebSocket connection failed: $ex")
  }

  // 监听 WebSocket 连接关闭事件
  closed.foreach(_ => println("WebSocket closed"))

  // 关闭 WebSocket 连接
  // closed.future.flatMap(_ => system.terminate())
}

上述代码示例中，首先创建了一个WebSocket消息处理器webSocketHandler，用于处理收到的WebSocket消息。然后使用Http().singleWebSocketRequest方法创建了一个WebSocket连接，并通过upgradeResponse获取连接的响应。如果连接成功，会打印"WebSocket connected"；如果连接失败，会打印"WebSocket connection failed"。同时，通过closed监听WebSocket连接关闭事件，在连接关闭时打印"WebSocket closed"。最后，可以使用closed.future.flatMap(_ => system.terminate())来关闭WebSocket连接和ActorSystem。

你可以根据实际情况修改WebSocket服务器地址、处理收到的WebSocket消息的逻辑，并根据需要处理连接失败和连接关闭事件。