// Copy request.
	req := *r

	// Save authorization header.
	v4Auth := req.Header.Get(xhttp.Authorization)

	// Parse signature version '4' header.
	signV4Values, errCode := parseSignV4(v4Auth, globalSite.Region(), serviceS3)
	if errCode != ErrNone {
		return cred, "", "", time.Time{}, errCode
	}

{!../../docs_src/middleware/tutorial001.py!}
```

/// tip | "Tipp"

Beachten Sie, dass benutzerdefinierte proprietäre Header hinzugefügt werden können. <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">Verwenden Sie dafür das Präfix 'X-'</a>.

        .build(),
    )
    newEventSource("text/plain")
    listener.assertOpen()
    listener.assertEvent(null, null, "hey")
    listener.assertClose()
    assertThat(server.takeRequest().headers["Accept"]).isEqualTo("text/plain")
  }

  @Test
  fun setsMissingAccept() {
    server.enqueue(
      MockResponse.Builder()
        .body(
          """
          |data: hey
          |

        length = 0,
        type = TYPE_SETTINGS,
        flags = FLAG_ACK,
      )
      sink.flush()
    }
  }

  /**
   * HTTP/2 only. Send a push promise header block.
   *
   * A push promise contains all the headers that pertain to a server-initiated request, and a
   * `promisedStreamId` to which response frames will be delivered. Push promise frames are sent as

* `content` – Ein `str` oder `bytes`.
* `status_code` – Ein `int`-HTTP-Statuscode.
* `headers` – Ein `dict` von Strings.
* `media_type` – Ein `str`, der den Medientyp angibt. Z. B. `"text/html"`.

FastAPI (eigentlich Starlette) fügt automatisch einen Content-Length-Header ein. Außerdem wird es einen Content-Type-Header einfügen, der auf dem media_type basiert, und für Texttypen einen Zeichensatz (charset) anfügen.

          if (streamId % 2 == nextStreamId % 2) return

          // Create a stream.
          val headers = headerBlock.toHeaders()
          val newStream = Http2Stream(streamId, this@Http2Connection, false, inFinished, headers)
          lastGoodStreamId = streamId
          streams[streamId] = newStream

    if current_user is None:
        return {"msg": "Create an account first"}
    return current_user


client = TestClient(app)


def test_security_api_key():
    response = client.get("/users/me", headers={"key": "secret"})
    assert response.status_code == 200, response.text
    assert response.json() == {"username": "secret"}


def test_security_api_key_no_key():
    response = client.get("/users/me")

	}, {
		header:  &Header{Mode: 07777777},
		formats: FormatUSTAR | FormatPAX | FormatGNU,
	}, {
		header:  &Header{Mode: 07777777 + 1},
		formats: FormatGNU,
	}, {
		header:  &Header{Devmajor: -123},
		formats: FormatGNU,
	}, {
		header:  &Header{Devmajor: 1<<56 - 1},
		formats: FormatGNU,
	}, {
		header:  &Header{Devmajor: 1 << 56},
		formats: FormatUnknown,
	}, {
		header:  &Header{Devmajor: -1 << 56},

        .build()
    val request =
      originalRequest.newBuilder()
        .header("Upgrade", "websocket")
        .header("Connection", "Upgrade")
        .header("Sec-WebSocket-Key", key)
        .header("Sec-WebSocket-Version", "13")
        .header("Sec-WebSocket-Extensions", "permessage-deflate")
        .build()
    call = RealCall(webSocketClient, request, forWebSocket = true)
    call!!.enqueue(

// For forward compatibility, users that retrieve a Header from Reader.Next,
// mutate it in some ways, and then pass it back to Writer.WriteHeader
// should do so by creating a new Header and copying the fields
// that they are interested in preserving.
type Header struct {
	// Typeflag is the type of header entry.
	// The zero value is automatically promoted to either TypeReg or TypeDir
	// depending on the presence of a trailing slash in Name.