*/
  fun cancel()

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

    // We post the event, but our Executor will not deliver it until instructed.
    bus.post(EVENT);

    List<String> events = catcher.getEvents();
    assertTrue("No events should be delivered synchronously.", events.isEmpty());

    // Now we find the task in our Executor and explicitly activate it.
    List<Runnable> tasks = executor.getTasks();
    assertEquals("One event dispatch task should be queued.", 1, tasks.size());

    title: JWT Authentication with FastAPI and AWS Cognito
  - author: Ankush Thakur
    author_link: https://geekflare.com/author/ankush/
    link: https://geekflare.com/python-asynchronous-web-frameworks/
    title: Top 5 Asynchronous Web Frameworks for Python
  - author: Nico Axtmann
    author_link: https://www.linkedin.com/in/nico-axtmann

& ⤴️ 👆 ✍ ❔ 🍵 [⚜ ⏮️ `CORSMiddleware`](../tutorial/cors.md){.internal-link target=_blank}.

👉 📄 👥 🔜 👀 ❔ ⚙️ 🎏 🛠️.

## ❎ 🔫 🛠️

**FastAPI** ⚓️ 🔛 💃 &amp; 🛠️ <abbr title="Asynchronous Server Gateway Interface">🔫</abbr> 🔧, 👆 💪 ⚙️ 🙆 🔫 🛠️.

🛠️ 🚫 ✔️ ⚒ FastAPI ⚖️ 💃 👷, 📏 ⚫️ ⏩ 🔫 🔌.

🏢, 🔫 🛠️ 🎓 👈 ⌛ 📨 🔫 📱 🥇 ❌.

, 🧾 🥉-🥳 🔫 🛠️ 👫 🔜 🎲 💬 👆 🕳 💖:

```Python

In this section we'll see how to use other middlewares.

## Adding ASGI middlewares

As **FastAPI** is based on Starlette and implements the <abbr title="Asynchronous Server Gateway Interface">ASGI</abbr> specification, you can use any ASGI middleware.

A middleware doesn't have to be made for FastAPI or Starlette to work, as long as it follows the ASGI spec.

Here's a little bit of that history.

## Alternatives

I have been creating APIs with complex requirements for several years (Machine Learning, distributed systems, asynchronous jobs, NoSQL databases, etc), leading several teams of developers.

As part of that, I needed to investigate, test and use many alternatives.

The history of **FastAPI** is in great part the history of its predecessors.

```Python hl_lines="1"
async def get_burgers(number: int):
    # Do some asynchronous stuff to create the burgers
    return burgers
```

...en vez de `def`:

```Python hl_lines="2"
# This is not asynchronous
def get_sequential_burgers(number: int):
    # Do some sequential stuff to create the burgers
    return burgers
```

要使 `await` 工作，它必须位于支持这种异步机制的函数内。因此，只需使用 `async def` 声明它：

```Python hl_lines="1"
async def get_burgers(number: int):
    # Do some asynchronous stuff to create the burgers
    return burgers
```

...而不是 `def`:

```Python hl_lines="2"
# This is not asynchronous
def get_sequential_burgers(number: int):
    # Do some sequential stuff to create the burgers
    return burgers
```

   dropped in 2.0.

## Version 1.5.4

_2014-04-14_

 * Drop ALPN support in Android. There's a concurrency bug in all
   currently-shipping versions.
 * Support asynchronous disconnects by breaking the socket only. This should
   prevent flakiness from multiple threads concurrently accessing a stream.

## Version 1.5.3

_2014-03-29_

 * ListenableFuture}</a>.
 *
 * <p>This class is GWT-compatible.
 *
 * <h3>Purpose</h3>
 *
 * <p>The main purpose of {@code ListenableFuture} is to help you chain together a graph of
 * asynchronous operations. You can chain them together manually with calls to methods like {@link
 * Futures#transform(ListenableFuture, com.google.common.base.Function, Executor) Futures.transform}