* @throws ArithmeticException if {@code mode} is {@link RoundingMode#UNNECESSARY} and {@code x}
   *     is not a power of two
   */
  @SuppressWarnings("fallthrough")
  // TODO(kevinb): remove after this warning is disabled globally
  public static int log2(BigInteger x, RoundingMode mode) {
    checkPositive("x", checkNotNull(x));
    int logFloor = x.bitLength() - 1;
    switch (mode) {
      case UNNECESSARY:

// built-in function recover.
//
// Starting in Go 1.21, calling panic with a nil interface value or an
// untyped nil causes a run-time error (a different panic).
// The GODEBUG setting panicnil=1 disables the run-time error.
func panic(v any)

// The recover built-in function allows a program to manage behavior of a
// panicking goroutine. Executing a call to recover inside a deferred

    input.addListener(output, rejectionPropagatingExecutor(executor, output));
    return output;
  }

  /*
   * In certain circumstances, this field might theoretically not be visible to an afterDone() call
   * triggered by cancel(). For details, see the comments on the fields of TimeoutFuture.
   */
  @LazyInit @Nullable ListenableFuture<? extends I> inputFuture;
  @LazyInit @Nullable F function;

      whether in tort (including negligence), contract, or otherwise,
      unless required by applicable law (such as deliberate and grossly
      negligent acts) or agreed to in writing, shall any Contributor be
      liable to You for damages, including any direct, indirect, special,
      incidental, or consequential damages of any character arising as a
      result of this License or out of the use or inability to use the

      whether in tort (including negligence), contract, or otherwise,
      unless required by applicable law (such as deliberate and grossly
      negligent acts) or agreed to in writing, shall any Contributor be
      liable to You for damages, including any direct, indirect, special,
      incidental, or consequential damages of any character arising as a
      result of this License or out of the use or inability to use the

      whether in tort (including negligence), contract, or otherwise,
      unless required by applicable law (such as deliberate and grossly
      negligent acts) or agreed to in writing, shall any Contributor be
      liable to You for damages, including any direct, indirect, special,
      incidental, or consequential damages of any character arising as a
      result of this License or out of the use or inability to use the

      whether in tort (including negligence), contract, or otherwise,
      unless required by applicable law (such as deliberate and grossly
      negligent acts) or agreed to in writing, shall any Contributor be
      liable to You for damages, including any direct, indirect, special,
      incidental, or consequential damages of any character arising as a
      result of this License or out of the use or inability to use the

///

<img src="/img/tutorial/security/image08.png">

呼叫端點 `/users/me/`，你會得到類似這樣的回應：

```JSON
{
  "username": "johndoe",
  "email": "******@****.***",
  "full_name": "John Doe",
  "disabled": false
}
```

<img src="/img/tutorial/security/image09.png">

如果你打開開發者工具，可以看到送出的資料只包含權杖；密碼只會在第一次請求（用來驗證使用者並取得 access token）時送出，之後就不會再送：

<img src="/img/tutorial/security/image10.png">

///

<img src="/img/tutorial/security/image08.png">

调用 `/users/me/` 端点，你将得到如下响应：

```JSON
{
  "username": "johndoe",
  "email": "******@****.***",
  "full_name": "John Doe",
  "disabled": false
}
```

<img src="/img/tutorial/security/image09.png">

如果你打开开发者工具，你会看到发送的数据只包含令牌。密码只会在第一个请求中用于认证用户并获取访问令牌，之后就不会再发送密码了：

<img src="/img/tutorial/security/image10.png">

/// note | 注意

var ntpServer = env.Get(ntpServerEnv, "")

// UTCNowNTP - is similar in functionality to UTCNow()
// but only used when we do not wish to rely on system
// time.
func UTCNowNTP() (time.Time, error) {
	// ntp server is disabled
	if ntpServer == "" {
		return time.Now().UTC(), nil
	}
	return ntp.Time(ntpServer)
}

// Retention - bucket level retention configuration.
type Retention struct {
	Mode        RetMode