```Python hl_lines="2-3"
@app.get('/burgers')
async def read_burgers():
    burgers = await get_burgers(2)
    return burgers
```

### More technical details

You might have noticed that `await` can only be used inside of functions defined with `async def`.

## HTTPX

Mesmo que a sua aplicação **FastAPI** utilize funções normais com `def` no lugar de `async def`, ela ainda é uma aplicação `async` por baixo dos panos.

Let's look at how we can make that work.

## pytest.mark.anyio

If we want to call asynchronous functions in our tests, our test functions have to be asynchronous. AnyIO provides a neat plugin for this, that allows us to specify that some test functions are to be called asynchronously.

## HTTPX

## HTTPX

Auch wenn Ihre **FastAPI**-Anwendung normale `def`-Funktionen anstelle von `async def` verwendet, handelt es sich darunter immer noch um eine `async`hrone Anwendung.

➖ 💪 ⚙️ 🔁 🔢 👆 💯 💪 ⚠, 🖼, 🕐❔ 👆 🔬 👆 💽 🔁. 🌈 👆 💚 💯 📨 📨 👆 FastAPI 🈸 & ⤴️ ✔ 👈 👆 👩‍💻 ⏪ ✍ ☑ 💽 💽, ⏪ ⚙️ 🔁 💽 🗃.

➡️ 👀 ❔ 👥 💪 ⚒ 👈 👷.

## pytest.mark.anyio

🚥 👥 💚 🤙 🔁 🔢 👆 💯, 👆 💯 🔢 ✔️ 🔁. AnyIO 🚚 👌 📁 👉, 👈 ✔ 👥 ✔ 👈 💯 🔢 🤙 🔁.

## 🇸🇲

🚥 👆 **FastAPI** 🈸 ⚙️ 😐 `def` 🔢 ↩️ `async def`, ⚫️ `async` 🈸 🔘.

    async.setFuture(inner);
    async.cancel(false);
    assertTrue(inner.isCancelled());
    assertFalse(inner.wasInterrupted());
    assertThrows(CancellationException.class, () -> inner.get());
  }

  public void testCancel_beforeSet() throws Exception {
    SettableFuture<Object> async = SettableFuture.create();
    async.cancel(true);
    assertFalse(async.set(42));
  }

    async.setFuture(inner);
    async.cancel(false);
    assertTrue(inner.isCancelled());
    assertFalse(inner.wasInterrupted());
    assertThrows(CancellationException.class, () -> inner.get());
  }

  public void testCancel_beforeSet() throws Exception {
    SettableFuture<Object> async = SettableFuture.create();
    async.cancel(true);
    assertFalse(async.set(42));
  }

        monkeypatch.delattr("multipart.multipart.parse_options_header", raising=False)
    with pytest.raises(RuntimeError, match=multipart_incorrect_install_error):
        app = FastAPI()

        @app.post("/")
        async def root(username: str = Form()):
            return username  # pragma: nocover


def test_incorrect_multipart_installed_file_upload(monkeypatch):
    monkeypatch.setattr("python_multipart.__version__", "0.0.12")

def test_merged_mixed_state_lifespans() -> None:
    @asynccontextmanager
    async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    @asynccontextmanager
    async def router_lifespan(app: FastAPI) -> AsyncGenerator[Dict[str, bool], None]:
        yield {"router": True}

    @asynccontextmanager
    async def sub_router_lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

The first thing to notice, is that we are defining an async function with `yield`. This is very similar to Dependencies with `yield`.

{* ../../docs_src/events/tutorial003.py hl[14:19] *}

The first part of the function, before the `yield`, will be executed **before** the application starts.

And the part after the `yield` will be executed **after** the application has finished.

### Async Context Manager