* the event source has already been closed or canceled.
   */
  fun cancel()

  fun interface Factory {
    /**
     * Creates a new event source and immediately returns it. Creating an event source initiates an
     * asynchronous process to connect the socket. Once that succeeds or fails, `listener` will be
     * notified. The caller must cancel the returned event source when it is no longer in use.
     */

    val startNanos = System.nanoTime()
    val call = client.newCall(request)

    // Schedule a job to cancel the call in 1 second.
    executor.schedule({
      System.out.printf("%.2f Canceling call.%n", (System.nanoTime() - startNanos) / 1e9f)
      call.cancel()
      System.out.printf("%.2f Canceled call.%n", (System.nanoTime() - startNanos) / 1e9f)
    }, 1, TimeUnit.SECONDS)

that by default Kotlin's Dispatchers are not used.

Cancellation if implemented sensibly in both directions.
Cancelling a coroutine scope, will cancel the call.
Cancelling a call, will throw a CancellationException

  /** Returns the trailers after the HTTP response. May be empty. */
  @Throws(IOException::class)
  fun trailers(): Headers

  /**
   * Cancel this stream. Resources held by this stream will be cleaned up, though not synchronously.
   * That may happen later by the connection pool thread.
   */
  fun cancel()

  /**
   * Carries an exchange. This is usually a connection, but it could also be a connect plan for

        exchange.bodyComplete<IOException?>(-1L, responseDone = true, requestDone = true, e = null)
      }

      override fun cancel() {
        exchange.cancel()
      }
    }
  }

  override fun route(): Route = route

  override fun cancel() {
    // Close the raw socket so we don't end up doing synchronous I/O.
    rawSocket?.closeQuietly()
  }

  override fun connectTcp() = error("already connected")

  override fun connectTlsEtc() = error("already connected")

  override fun handleSuccess() = connection

  override fun cancel() = error("unexpected cancel")

  override fun retry() = error("unexpected retry")

        override fun dispatch(request: RecordedRequest): MockResponse {
          call.cancel()
          return MockResponse(body = "A")
        }
      }
    call.enqueue(callback)
    assertThat(server.takeRequest().path).isEqualTo("/a")
    callback.await(requestA.url).assertFailure(
      "Canceled",
      "stream was reset: CANCEL",
      "Socket closed",
    )
  }

  @Test

   * exception.
   *
   * @throws IllegalStateException when the call has already been executed.
   */
  fun enqueue(responseCallback: Callback)

  /** Cancels the request, if possible. Requests that are already complete cannot be canceled. */
  fun cancel()

  /**
   * Returns true if this call has been either [executed][execute] or [enqueued][enqueue]. It is an
   * error to execute a call more than once.
   */

    override fun dispatch(request: RecordedRequest): MockResponse {
      // This guarantees a deterministic sequence when handling the canceled request:
      // 1. Server reads request and dequeues first response
      // 2. Client cancels request
      // 3. Server tries to send response on the canceled stream
      // Otherwise, there is no guarantee for the sequence. For example, the server may use the

        .build(),
    )
    listener.enqueueCancel() // Will cancel in onOpen().
    val request =
      Request.Builder()
        .url(server.url("/"))
        .build()
    val response = client.newCall(request).execute()
    processResponse(response, listener)
    listener.assertOpen()
    listener.assertFailure("canceled")
  }