*   <li>calls {@link ExecutorService#shutdown()}, disabling acceptance of new submitted tasks.
   *   <li>awaits executor service termination for half of the specified timeout.
   *   <li>if the timeout expires, it calls {@link ExecutorService#shutdownNow()}, cancelling
   *       pending tasks and interrupting running tasks.
   *   <li>awaits executor service termination for the other half of the specified timeout.
   * </ol>
   *

    public @Nullable Void call() throws InterruptedException {
      running = true;
      startLatch.countDown();
      stopLatch.await();
      running = false;
      return null;
    }

    public void waitForStart() throws InterruptedException {
      startLatch.await();
    }

    public void stop() {
      stopLatch.countDown();
    }

    public boolean isRunning() {

individual, or aggression toward or disparagement of classes of individuals.

**Consequence**: A permanent ban from any sort of public interaction within
the community.

## Attribution

This Code of Conduct is adapted from the [Contributor Covenant][homepage],
version 2.0, available at
https://www.contributor-covenant.org/version/2/0/code_of_conduct.html.

Community Impact Guidelines were inspired by [Mozilla's code of conduct

/// info | "说明"

`open()` 函数中，`mode="a"` 指的是**追加**。因此这行文本会添加在文件已有内容之后，不会覆盖之前的内容。

///

/// tip | "提示"

注意，本例使用 Python `open()` 标准函数与文件交互。

这个函数执行 I/O（输入/输出）操作，需要等待内容写进磁盘。

但 `open()` 函数不支持使用 `async` 与 `await`。

因此，声明事件处理函数要使用 `def`，不能使用 `asnyc def`。

///

/// info | "说明"

有关事件处理器的详情，请参阅 <a href="https://www.starlette.io/events/" class="external-link" target="_blank">Starlette 官档 - 事件</a>。

        router = APIRouter()

        @router.websocket("/ws")
        async def websocket_endpoint(websocket: WebSocket):
            await websocket.accept()
            while True:
                data = await websocket.receive_text()
                await websocket.send_text(f"Message text was: {data}")

        app.include_router(router)
        ```
        """

```

/// note | "技術詳細"

`from starlette.websockets import WebSocket` を使用しても構いません.

**FastAPI** は開発者の利便性のために、同じ `WebSocket` を提供します。しかし、こちらはStarletteから直接提供されるものです。

///

## メッセージの送受信

WebSocketルートでは、 `await` を使ってメッセージの送受信ができます。

```Python hl_lines="48-52"
{!../../docs_src/websockets/tutorial001.py!}
```

バイナリやテキストデータ、JSONデータを送受信できます。

## 試してみる

ファイル名が `main.py` である場合、以下の方法でアプリケーションを実行します。

   *
   * @param reference any array of the desired type
   * @param length the length of the new array
   */
  /*
   * The new array contains nulls, even if the old array did not. If we wanted to be accurate, we
   * would declare a return type of `@Nullable T[]`. However, we've decided not to think too hard
   * about arrays for now, as they're a mess. (We previously discussed this in the review of

   *
   * @param reference any array of the desired type
   * @param length the length of the new array
   */
  /*
   * The new array contains nulls, even if the old array did not. If we wanted to be accurate, we
   * would declare a return type of `@Nullable T[]`. However, we've decided not to think too hard
   * about arrays for now, as they're a mess. (We previously discussed this in the review of

	expected := false
	if locked != expected {
		t.Errorf("TestDualWriteLockTimedOut(): \nexpected %#v\ngot      %#v", expected, locked)
	}
}

// Test cases below are copied 1 to 1 from sync/rwmutex_test.go (adapted to use DRWMutex)

// Borrowed from rwmutex_test.go
func parallelReader(ctx context.Context, m *DRWMutex, clocked, cunlock, cdone chan bool) {
	if m.GetRLock(ctx, nil, id, source, Options{Timeout: time.Second}) {

with open("file.txt") as file:
    file.read()
```

In neueren Versionen von Python gibt es auch einen **asynchronen Kontextmanager**. Sie würden ihn mit `async with` verwenden:

```Python
async with lifespan(app):
    await do_stuff()
```