@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

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

If your code uses `async` / `await`, use `async def`:

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

from fastapi import FastAPI

app = FastAPI()


@app.get("/")

### Canceling a Call ([.kt][CancelCallKotlin], [.java][CancelCallJava])

Use `Call.cancel()` to stop an ongoing call immediately. If a thread is currently writing a request or reading a response, it will receive an `IOException`. Use this to conserve the network when a call is no longer necessary; for example when your user navigates away from an application. Both synchronous and asynchronous calls can be canceled.

)

const (
	defaultBufSize = 4096
)

var (
	ErrInvalidUnreadByte = errors.New("bufio: invalid use of UnreadByte")
	ErrInvalidUnreadRune = errors.New("bufio: invalid use of UnreadRune")
	ErrBufferFull        = errors.New("bufio: buffer full")
	ErrNegativeCount     = errors.New("bufio: negative count")
)

// Buffered input.

// Reader implements buffering for an io.Reader object.

        return ch >= 32 && ch < 127;
    }

    /**
     * Creates a new String from a char array without copying the array.
     * <p>
     * This method uses internal JDK APIs and may not be available in all Java versions.
     * If the internal API is not available, it falls back to the standard String constructor.
     * </p>
     *
     * @param chars

    continuation.length = continuation.left
    continuation.padding = padding
    continuation.flags = flags
    continuation.streamId = streamId

    // TODO: Concat multi-value headers with 0x0, except COOKIE, which uses 0x3B, 0x20.
    // http://tools.ietf.org/html/draft-ietf-httpbis-http2-17#section-8.1.2.5
    hpackReader.readHeaders()
    return hpackReader.getAndResetHeaderList()
  }

  @Throws(IOException::class)

It allows a counting semaphore to be modeled by a buffered channel:
the number of items in the channel corresponds to the number of active uses,
the capacity of the channel corresponds to the maximum number of simultaneous uses,
sending an item acquires the semaphore, and receiving an item releases
the semaphore.
This is a common idiom for limiting concurrency.
</p>

<p>

   *       is used to construct the sample instances. In case of tie, the candidate constructors or
   *       factories are tried one after another until one can be used to construct sample
   *       instances.
   *   <li>For the constructor or static factory method used to construct instances, it's checked

 *
 * <p><b>For users targeting Android API level 24 or higher:</b> This class will eventually
 * implement {@code BiPredicate<T, T>} (as it does in the main Guava artifact), but we currently
 * target a lower API level. In the meantime, if you have support for method references you can use
 * an equivalence as a bi-predicate like this: {@code myEquivalence::equivalent}.
 *

- kube-apiserver:

>
> ```
> host                (hostname)           Postgres server hostname (used only if `connection_string` is empty)
> port                (port)               Postgres server port, defaults to `5432` (used only if `connection_string` is empty)
> username            (string)             database username (used only if `connection_string` is empty)