我如何访问golang中的错误个别属性

Question

我正在使用数据同步 API 开始执行任务，没有任何问题。我正在努力处理返回的错误结构，我想访问单个元素，但我似乎无法这样做。例如在以下错误中我希望能够访问Message_的内容2022/03/19 09:33:48 Sync called : InvalidRequestException: Unable to queue the task execution for task task-xxxxxxxxxxxx. The task already has another task execution exec-030b4a31dc2e33641 currently running or queued with identical Include and Exclude filter patterns. Please provide unique Include and Exclude filter patterns for the new task execution and try again.{  RespMetadata: {    StatusCode: 400,    RequestID: "xxxxxxxxxxxxxxxxxxxxx"  },  ErrorCode: "DedupeFailed",  Message_: "Unable to queue the task execution for task task-xxxxxxxxxx. The task already has another task execution exec-xxxxxxxxxx currently running or queued with identical Include and Exclude filter patterns. Please provide unique Include and Exclude filter patterns for the new task execution and try again."}这是我的工作示例：    // Create datasync service client    svc := datasync.New(sess)    params := &datasync.StartTaskExecutionInput{        TaskArn : aws.String("arn:aws:datasync:*******************************"),    }    // start task execution    resp, err := svc.StartTaskExecution(params)    //err = req.Send()    if err == nil { // resp is now filled        fmt.Println(resp)  // this outputs this { TaskExecutionArn: "arn:aws:datasync:xxxxxxxx:task/task-03ecb7728e984e36a/execution/exec-xxxxxxxxxx" }    } else {        fmt.Println(err)        //fmt.Println(err.Message()) THIS DOES NOT WORK        //fmt.Println(err.Message_)  THIS ALSO DOES NOT WORK    }如果我这样做fmt.Println(err.Message())或者this fmt.Println(err.Message_)我得到这个error  err.Message undefined (type error has no field or method Message) err.Message_ undefined (type error has no field or method Message_)我哪里做错了 ？

Answer 1

AWS SDK for Go 中的错误通常是接口错误awserr.Error（Github 上的代码）。

如果你只想收到消息，你可以这样做：

resp, err := svc.StartTaskExecution(params)

if err != nil {

    if awsErr, ok := err.(awserr.Error); ok {

        fmt.Println(awsErr.Message())

    } else {

        fmt.Println(err.Error())

    }

}

首先，检查是否确实存在错误：

if err != nil {...}

然后，我们尝试将错误转换为特定的“类型” awserr.Error：

err.(awserr.Error)

cast 的返回值是特定的错误awsErr和一个bool指示 cast 是否有效的值 ( ok)。

awsErr, ok := err.(awserr.Error)

其余代码基本上只是检查，如果ok == true是这种情况，您可以访问错误字段，例如Message：

if awsErr, ok := err.(awserr.Error); ok {

    fmt.Println(awsErr.Message())

}

否则，您只需打印标准的 Go 错误消息：

if awsErr, ok := err.(awserr.Error); ok {

    ...

} else {

    fmt.Println(err.Error())

}