ctx, cancel := context.WithCancel(context.Background())
	go func() {
		select {
		case <-ctx1.Done():
		case <-ctx2.Done():
		// The lock acquirer decides to cancel, exit this goroutine
		case <-ctx.Done():
		}

		cancel()
	}()
	return ctx, cancel
}

func (ld sharedLock) GetLock(ctx context.Context) (context.Context, context.CancelFunc) {

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder
from pydantic import BaseModel

fake_db = {}


class Item(BaseModel):
    title: str
    timestamp: datetime
    description: str | None = None


app = FastAPI()


@app.put("/items/{id}")
def update_item(id: str, item: Item):
    json_compatible_item_data = jsonable_encoder(item)

		maxEntries = opts.count
	}

	done := false
	remaining := opts.count

	for !done {
		// Read up to max number of entries.
		fis, err := d.Readdir(maxEntries)
		if err != nil {
			if err == io.EOF {
				break
			}
			return nil, osErrToFileErr(err)
		}
		if opts.count > -1 {
			if remaining <= len(fis) {
				fis = fis[:remaining]
				done = true
			}
		}

* 如果该参数也在**路径**中声明了，它就是路径参数。
* 如果该参数是（`int`、`float`、`str`、`bool` 等）**单一类型**，它会被当作**查询**参数。
* 如果该参数的类型声明为 **Pydantic 模型**，它会被当作请求**体**。

/// note | 注意

FastAPI 会根据默认值 `= None` 知道 `q` 的值不是必填的。

`str | None` 并不是 FastAPI 用来判断是否必填的依据；是否必填由是否有默认值 `= None` 决定。

但添加这些类型注解可以让你的编辑器提供更好的支持并检测错误。

///

## 不使用 Pydantic { #without-pydantic }

        assertFalse(cos.done);
        assertTrue(cos.isInMemory());
        cos.close();
        assertFalse(cos.done);
    }

    @Test
    public void inFile() throws IOException {
        ContentOutputStream cos = new ContentOutputStream(10, Curl.tmpDir);
        cos.write(new byte[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 });
        assertFalse(cos.done);
        assertFalse(cos.isInMemory());

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[
        str | None,
        Query(
            title="Query string",
            description="Query string for the items to search in the database that have a good match",
            min_length=3,
        ),
    ] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

        summary: str | None = None,
        description: str | None = None,
        response_description: str = "Successful Response",
        responses: dict[int | str, dict[str, Any]] | None = None,
        deprecated: bool | None = None,
        name: str | None = None,
        methods: set[str] | list[str] | None = None,
        operation_id: str | None = None,
        response_model_include: IncEx | None = None,

	// apply len2 zeros to crc1 (first square will put the operator for one
	// zero byte, eight zero bits, in even)
	crc1n := uint64(crc1)
	for {
		// apply zeros operator for this bit of len2
		gf2MatrixSquare(even, odd)
		if len2&1 != 0 {
			crc1n = gf2MatrixTimes(even, crc1n)
		}
		len2 >>= 1

		// if no more bits set, then done
		if len2 == 0 {
			break
		}

    Object one = new Object();
    assertThat(map.put(one, one)).isNull();
    assertThat(map.get(one)).isSameInstanceAs(one);
    assertThat(map.containsKey(one)).isTrue();
    assertThat(map.containsValue(one)).isTrue();
    Object two = new Object();
    assertThat(map.replace(one, two)).isSameInstanceAs(one);
    assertThat(map.containsKey(one)).isTrue();

    Object one = new Object();
    assertThat(map.put(one, one)).isNull();
    assertThat(map.get(one)).isSameInstanceAs(one);
    assertThat(map.containsKey(one)).isTrue();
    assertThat(map.containsValue(one)).isTrue();
    Object two = new Object();
    assertThat(map.replace(one, two)).isSameInstanceAs(one);
    assertThat(map.containsKey(one)).isTrue();