fastFailHttpClient := &http.Client{Timeout: time.Second * 2}
resp, httpErr = ad.fastFailHttpClient.Do(req)
    if httpErr != nil || resp == nil || resp.StatusCode == 404 {
       // 建议重试
    }
    defer func() { _ = resp.Body.Close() }()
    break
}
if httpErr != nil || resp == nil {
    //
}
respCode = resp.StatusCode
if respCode == 200 {
    tmpBody, errRead := ioutil.ReadAll(resp.Body)
    if errRead != nil {
        logger.Error("read resp error", zap.String("err", errRead.Error())) //日志中错误:net/http: request canceled (Client.Timeout exceeded while reading body)
        return
    }

type Client struct {
	// Timeout specifies a time limit for requests made by this
	// Client. The timeout includes connection time, any
	// redirects, and reading the response body. The timer remains
	// running after Get, Head, Post, or Do return and will
	// interrupt reading of the Response.Body. (这里说了,如果超时,会中断do和read body操作)
	//
	// A Timeout of zero means no timeout.
	//
	// The Client cancels requests to the underlying Transport
	// as if the Request's Context ended.
	//
	// For compatibility, the Client will also use the deprecated
	// CancelRequest method on Transport if found. New
	// RoundTripper implementations should use the Request's Context
	// for cancellation instead of implementing CancelRequest.
	Timeout time.Duration
}