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

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

   * calls returns to zero).
   *
   * Note: The time at which a [call][Call] is considered idle is different depending on whether it
   * was run [asynchronously][Call.enqueue] or [synchronously][Call.execute]. Asynchronous calls
   * become idle after the [onResponse][Callback.onResponse] or [onFailure][Callback.onFailure]
   * callback has returned. Synchronous calls become idle once [execute()][Call.execute] returns.

	v := t.val.Load()
	ttl := t.ttl
	vTime := t.lastUpdateMs.Load()
	tNow := time.Now().UnixMilli()
	if v != nil && tNow-vTime < ttl.Milliseconds() {
		return *v, nil
	}

	// Fetch new value asynchronously, while we do not return an error
	// if v != nil value or
	if t.opts.NoWait && v != nil && tNow-vTime < ttl.Milliseconds()*2 {
		if t.updating.TryLock() {
			go func() {
				defer t.updating.Unlock()

    final NoOpService service1 = new NoOpService();
    // This service will start service1 when addListener is called.  This simulates service1 being
    // started asynchronously.
    Service service2 =
        new Service() {
          final NoOpService delegate = new NoOpService();

          @Override
          public final void addListener(Listener listener, Executor executor) {

 *         } catch (TimeoutException timeout) {
 *           // stopping timed out
 *         }
 *       }
 *     });
 *     manager.startAsync();  // start all the services asynchronously
 *   }
 * }
 * }</pre>
 *
 * <p>This class uses the ServiceManager's methods to start all of its services, to respond to

 *         } catch (TimeoutException timeout) {
 *           // stopping timed out
 *         }
 *       }
 *     });
 *     manager.startAsync();  // start all the services asynchronously
 *   }
 * }
 * }</pre>
 *
 * <p>This class uses the ServiceManager's methods to start all of its services, to respond to

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A step in a pipeline of an asynchronous computation. When the last step in the computation is
 * complete, some objects captured during the computation are closed.
 *
 * <p>A pipeline of {@code ClosingFuture}s is a tree of steps. Each step represents either an
 * asynchronously-computed intermediate value, or else an exception that indicates the failure or

  // re-use a thread.
  std::vector<std::unique_ptr<DeviceThread>> device_threads_;
  // A cancellation manager to use if the caller does not provide one. When ops
  // are executed asynchronously this must outlive the queued op, so it can't be
  // function-local to Execute.
  mutable std::unique_ptr<CancellationManager> default_cancellation_manager_;
};

/// 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`

Asynchronously streams a file as the response.

Takes a different set of arguments to instantiate than the other response types:

* `path` - The file path to the file to stream.

    return (FluentFuture<V>) Futures.withTimeout(this, timeout, unit, scheduledExecutor);
  }

  /**
   * Returns a new {@code Future} whose result is asynchronously derived from the result of this
   * {@code Future}. If the input {@code Future} fails, the returned {@code Future} fails with the
   * same exception (and the function is not invoked).
   *