.url(url)
        .build()

    val promise = CompletableFuture<Response>()

    val call = client.newCall(request)
    call.enqueue(
      object : Callback {
        override fun onFailure(
          call: Call,
          e: IOException,
        ) {
          promise.completeExceptionally(e)
        }

        override fun onResponse(
          call: Call,
          response: Response,

    would never call back if it crashed with an unchecked throwable, such as a
    `NullPointerException` or `OutOfMemoryError`. We now call `Callback.onFailure()` with an
    `IOException` that reports the call as canceled. The triggering exception is still delivered to
    the thread's `UncaughtExceptionHandler`.

        if (failure != null) {
          callback.onFailure(failure);
          return;
        }
      }
      V value;
      try {
        value = getDone(future);
      } catch (ExecutionException e) {
        callback.onFailure(e.getCause());
        return;
      } catch (Throwable e) {

    failures: MutableList<Exception>,
  ) {
    val latch = CountDownLatch(networkRequests.size)

    for (call in networkRequests) {
      call.enqueue(
        object : Callback {
          override fun onFailure(
            call: Call,
            e: IOException,
          ) {
            synchronized(failures) {
              failures.add(e)
            }
            latch.countDown()
          }

        override fun clone(): Call = TODO()
      }
  }

  @Test
  fun callback() {
    val callback =
      object : Callback {
        override fun onFailure(
          call: Call,
          e: IOException,
        ) = TODO()

        override fun onResponse(
          call: Call,
          response: Response,
        ) = TODO()
      }
  }

 *   public void onResponse(Call call, Response response) throws IOException {
 *     try (ResponseBody responseBody = response.body()) {
 *     ... // Use the response.
 *     }
 *   }
 *
 *   public void onFailure(Call call, IOException e) {
 *   ... // Handle the failure.
 *   }
 * });
 * ```
 *
 * These examples will not work if you're consuming the response body on another thread. In such

          .Builder()
          .url(server.url("/"))
          .build(),
      )
    val completionLatch = CountDownLatch(1)
    val callback: Callback =
      object : Callback {
        override fun onFailure(
          call: Call,
          e: IOException,
        ) {
          completionLatch.countDown()
        }

        override fun onResponse(
          call: Call,
          response: Response,

    the client.

 *  **WebSocketListener has incompatible changes.** The `onOpen()` method is now
    called on the reader thread, so implementations must return before further
    websocket messages will be delivered. The `onFailure()` method now includes
    an HTTP response if one was returned.

## Version 2.4.0-RC1

_2015-05-16_

 *  **New HttpUrl API.** It's like `java.net.URL` but good. Note that

            throw AssertionError(e)
          }
          assert200Http2Response(response, "san.com")
          connection.get()!!.socket().close()
          latch4.countDown()
        }

        override fun onFailure(
          call: Call,
          e: IOException,
        ) {
          fail("")
        }
      },
    )
    val client2 =
      client
        .newBuilder()

    requestCanceledLatch: CountDownLatch?,
  ) {
    val call = client.newCall(Request(server.url("/")))
    val latch = CountDownLatch(1)
    call.enqueue(
      object : Callback {
        override fun onFailure(
          call: Call,
          e: IOException,
        ) {
          latch.countDown()
        }

        override fun onResponse(
          call: Call,
          response: Response,