def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>O usa <code>async def</code>...</summary>

Si tu código usa `async` / `await`, usa `async def`:

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_root():
    return {"Hello": "World"}

def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>或可以使用 <code>async def</code>...</summary>

如果你的程式使用 `async` / `await`，請使用 `async def`：

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_root():
    return {"Hello": "World"}

def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Ou use <code>async def</code>...</summary>

Se seu código utiliza `async` / `await`, use `async def`:

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_root():
    return {"Hello": "World"}

Não faz diferença. O **FastAPI** sabe o que fazer.

/// note | Nota

Caso você não conheça, veja em [Async: *"Com Pressa?"*](../../async.md#in-a-hurry){.internal-link target=_blank} a sessão acerca de `async` e `await` na documentação.

///

## Integrando com OpenAPI { #integrated-with-openapi }

 * code changes, you can use <a
 * href="https://www.javadoc.io/doc/com.github.ben-manes.caffeine/guava/latest/com.github.benmanes.caffeine.guava/com/github/benmanes/caffeine/guava/CaffeinatedGuava.html">its
 * {@code CaffeinatedGuava} adapter class</a>, which lets you build a Guava {@code Cache} or a Guava
 * {@code LoadingCache} backed by a Guava {@code CacheLoader}.
 *
 * <p>Caffeine's API for asynchronous operations uses {@code CompletableFuture}: <a

/// tip | Consejo

Nota que aquí como estamos usando `open()` estándar que no admite `async` y `await`, declaramos el path operation con `def` normal.

///

### `FileResponse` { #fileresponse }

Transmite un archivo asincrónicamente como response.

    val request = Request.Builder().url("https://www.howsmyssl.com/a/check").build()

    val response = client.newCall(request).execute()

    val results =
      response.use {
        moshi.adapter(HowsMySslResults::class.java).fromJson(response.body.string())!!
      }

    Platform.get().log("results $results", Platform.WARN)

    assertTrue(results.session_ticket_supported)

Darum müssen wir es in diesem Fall im `response_model`-Parameter deklarieren.

... aber lesen Sie weiter, um zu sehen, wie man das anders lösen kann.

## Rückgabewert und Datenfilterung { #return-type-and-data-filtering }

                } finally {
                    latch.countDown();
                }
            });
        }

        latch.await(5, TimeUnit.SECONDS);
        executor.shutdown();

        // Verify all listeners were added
        assertEquals(numThreads, fesenClient.onConnectListenerList.size());
    }

    /**

                } else {
                    latch.countDown();
                }
            }
            try {
                latch.await();
            } catch (InterruptedException e) {
                result.addErrorArtifactException(
                        new ArtifactResolutionException("Resolution interrupted", rootArtifact, e));
            }