Bagaimana untuk mengendalikan ralat HTTP di Golang?

import "net/http"

var (
    ErrBadRequest       = http.StatusBadRequest
    ErrUnauthorized     = http.StatusUnauthorized
    ErrForbidden        = http.StatusForbidden
    ErrNotFound         = http.StatusNotFound
    ErrMethodNotAllowed = http.StatusMethodNotAllowed
)

type MyError struct {
    code    int
    message string
}

func (e *MyError) Error() string {
    return fmt.Sprintf("code: %d, message: %s", e.code, e.message)
}

func HandleRequest(w http.ResponseWriter, r *http.Request) {
    if err := validateRequest(r); err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }

    // ... 继续处理请求
}

err := httputil.NewError(http.StatusBadRequest, "Bad Request")

func HandleRequest(w http.ResponseWriter, r *http.Request) {
    switch r.Method {
    case "GET":
        // ... 处理 GET 请求
    case "POST":
        // ... 处理 POST 请求
    default:
        http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
    }
}

type InvalidRequestError struct {
    message string
}

func (e InvalidRequestError) Error() string {
    return fmt.Sprintf("invalid request: %s", e.message)
}

func HandleRequest(w http.ResponseWriter, r *http.Request) {
    if err := validateRequest(r); err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }

    // ... 继续处理请求
}