var c *metacache
		if rpc == nil {
			resp := localMetacacheMgr.getBucket(ctx, o.Bucket).findCache(*o)
			c = &resp
		} else {
			rctx, cancel := context.WithTimeout(ctx, 5*time.Second)
			c, err = rpc.GetMetacacheListing(rctx, *o)
			cancel()
		}
		if err != nil {
			if errors.Is(err, context.Canceled) {
				// Context is canceled, return at once.

	if endpoint == "" {
		return nil
	}

	buf, err := json.Marshal(ri)
	if err != nil {
		return err
	}

	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(buf))
	if err != nil {
		return err
	}

	if token != "" {

你可以创建一个第一层依赖项（“dependable”），如下：

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

这段代码声明了类型为 `str` 的可选查询参数 `q`，然后返回这个查询参数。

这个函数很简单（不过也没什么用），但却有助于让我们专注于了解子依赖项的工作方式。

## 第二层依赖项，“dependable”和“dependant” { #second-dependency-dependable-and-dependant }

接下来，创建另一个依赖项函数（一个“dependable”），并同时为它自身再声明一个依赖项（因此它同时也是一个“dependant”）：

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[13] *}

这里重点说明一下声明的参数：

	if err != nil {
		t.Fatalf("unable create credential, %s", err)
	}

	globalActiveCred = creds

	globalIAMSys.Init(ctx, objLayer, globalEtcdClient, 2*time.Second)

	// List of test cases for validating http request authentication.
	testCases := []struct {
		req     *http.Request
		s3Error APIErrorCode
	}{
		// When request is unsigned, access denied is returned.

	var allVersionIDs, freeVersionIDs []string
	for i := range 5 {
		fi := basefi
		fi.VersionID = mustGetUUID()
		fi.DataDir = mustGetUUID()
		fi.ModTime = basefi.ModTime.Add(time.Duration(i) * time.Second)
		if err := xl.AddVersion(fi); err != nil {
			t.Fatalf("%d: Failed to add version %v", i+1, err)
		}

		if i > 3 {
			// Simulate transition of a version
			transfi := fi

	}
}

func TestTransactionWithDefaultTimeout(t *testing.T) {
	db, err := OpenTestConnection(&gorm.Config{DefaultTransactionTimeout: 2 * time.Second})
	if err != nil {
		t.Fatalf("failed to connect database, got error %v", err)
	}

	tx := db.Begin()
	time.Sleep(3 * time.Second)
	if err = tx.Find(&User{}).Error; err == nil {
		t.Errorf("should return error when transaction timeout, got error %v", err)
	}

	}

	u := url.URL(*o.args.URL)
	q := u.Query()
	q.Set("token", token)
	u.RawQuery = q.Encode()

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u.String(), nil)
	if err != nil {
		return AuthNResponse{}, err
	}

	if o.args.AuthToken != "" {

		}
		return info, nil
	} // In all other cases cache the value upto 1sec.

	client.diskInfoCache.InitOnce(time.Second, cachevalue.Opts{},
		func(ctx context.Context) (info DiskInfo, err error) {
			ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
			defer cancel()

			nopts := DiskInfoOptions{DiskID: *client.diskID.Load(), Metrics: true}

and Alice's first thought was that it might belong to one of the
doors of the hall; but, alas! either the locks were too large, or
the key was too small, but at any rate it would not open any of
them.  However, on the second time round, she came upon a low
curtain she had not noticed before, and behind it was a little
door about fifteen inches high:  she tried the little golden key
in the lock, and to her great delight it fitted!

		},
		{
			reqURL:    "http://127.0.0.1:8443/?DurationSeconds=800",
			expectErr: true,
		},
		{
			reqURL:   "http://127.0.0.1:8443/?DurationSeconds=901",
			duration: time.Duration(901) * time.Second,
		},
	}

	for i, testCase := range testCases {
		u, err := url.Parse(testCase.reqURL)
		if err != nil {
			t.Fatal(err)
		}
		d, err := GetDefaultExpiration(u.Query().Get("DurationSeconds"))