/// tip

Notice that here as we are using standard `open()` that doesn't support `async` and `await`, we declare the path operation with normal `def`.

///

### `FileResponse` { #fileresponse }

Asynchronously streams a file as the response.

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

<details markdown="1">
<summary>Tàbí lò <code>async def</code>...</summary>

Tí kóòdù rẹ̀ bá ń lò `async` / `await`, lò `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"}

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

				throw new Error("total length of command line and environment variables exceeds limit");
			}

			this._inst.exports.run(argc, argv);
			if (this.exited) {
				this._resolveExitPromise();
			}
			await this._exitPromise;
		}

		_resume() {
			if (this.exited) {
				throw new Error("Go program has already exited");
			}
			this._inst.exports.resume();
			if (this.exited) {

                    errorCount.incrementAndGet();
                } finally {
                    latch.countDown();
                }
            }).start();
        }

        try {
            latch.await();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            fail("Thread safety test interrupted");
        }

      futures.add(
          executor.submit(
              new Callable<@Nullable Void>() {
                @Override
                public @Nullable Void call() throws Exception {
                  barrier.await();
                  Integer first = network.nodes().iterator().next();
                  for (Integer node : network.nodes()) {
                    Set<Integer> unused = network.successors(node);
                  }

    }

    // 0x4f 0x4b 0x6f 0x6b is "OKok".
    writePing(false, AWAIT_PING, 0x4f4b6f6b)
  }

  /** For testing: awaits a pong. */
  @Throws(InterruptedException::class)
  fun awaitPong() {
    withLock {
      while (awaitPongsReceived < awaitPingsSent) {
        wait()
      }
    }
  }

  @Throws(IOException::class)
  fun flush() {
    writer.flush()
  }

  /**

/// tip | Dica

Perceba que aqui estamos utilizando o `open()` da biblioteca padrão que não suporta `async` e `await`, e declaramos a operação de rota com o `def` básico.

///

### `FileResponse`

Envia um arquivo  de forma assíncrona e contínua (stream).
*

  }

  /** For testing: force this web socket to release its threads. */
  @Throws(InterruptedException::class)
  fun tearDown() {
    taskQueue.shutdown()
    taskQueue.idleLatch().await(10, TimeUnit.SECONDS)
  }

  @Synchronized fun sentPingCount(): Int = sentPingCount

  @Synchronized fun receivedPingCount(): Int = receivedPingCount

        override fun responseHeadersEnd(
          call: Call,
          response: Response,
        ) {
          try {
            // Wait for the server to send the duplex response before acting on the 301 response
            // and resetting the stream.
            duplexResponseSent.await()
          } catch (e: InterruptedException) {
            throw AssertionError()
          }