如何自定义Golang错误类型 实现带有上下文信息的错误结构

error

errors.New

fmt.Errorf

package main

import (
    "fmt"
    "runtime"
    "time"
)

type MyError struct {
    Code    int       // 错误码
    Msg     string    // 错误消息
    Details string    // 详细描述
    Time    time.Time // 发生时间
    File    string    // 出错文件
    Line    int       // 出错行号
    TraceID string    // 请求追踪ID
}

func (e *MyError) Error() string {
    return fmt.Sprintf("[%s] ERROR %d: %s (details: %s) at %s:%d traceID=%s",
        e.Time.Format("2006-01-02 15:04:05"),
        e.Code,
        e.Msg,
        e.Details,
        e.File,
        e.Line,
        e.TraceID,
    )
}

error

Error() string

func NewMyError(code int, msg, details, traceID string) *MyError {
    _, file, line, _ := runtime.Caller(1) // 调用者的文件和行号
    return &MyError{
        Code:    code,
        Msg:     msg,
        Details: details,
        Time:    time.Now(),
        File:    file,
        Line:    line,
        TraceID: traceID,
    }
}

runtime.Caller(1)

1

func getData() error {
    return NewMyError(1001, "failed to fetch data", "network timeout", "req-12345")
}

func processData() error {
    err := getData()
    if err != nil {
        // 可以包装或透传
        return NewMyError(2001, "process failed", err.Error(), "req-12345")
    }
    return nil
}

func main() {
    err := processData()
    if err != nil {
        fmt.Println(err)
        // 输出示例：
        // [2025-04-05 10:00:00] ERROR 2001: process failed (details: [2025-04-05 10:00:00] ERROR 1001: failed to fetch data (details: network timeout) at main.go:30 traceID=req-12345) at main.go:40 traceID=req-12345
    }
}

%w

type MyError struct {
    Code    int
    Msg     string
    Details string
    Time    time.Time
    File    string
    Line    int
    TraceID string
    Cause   error // 包装原始错误
}

func (e *MyError) Error() string {
    if e.Cause != nil {
        return fmt.Sprintf("[%s] ERROR %d: %s (details: %s) at %s:%d traceID=%s -> caused by: %v",
            e.Time.Format("2006-01-02 15:04:05"),
            e.Code,
            e.Msg,
            e.Details,
            e.File,
            e.Line,
            e.TraceID,
            e.Cause,
        )
    }
    return fmt.Sprintf("[%s] ERROR %d: %s (details: %s) at %s:%d traceID=%s",
        e.Time.Format("2006-01-02 15:04:05"),
        e.Code,
        e.Msg,
        e.Details,
        e.File,
        e.Line,
        e.TraceID,
    )
}

// 实现 Unwrap 方法，支持 errors.Is 和 errors.As
func (e *MyError) Unwrap() error {
    return e.Cause
}

// 修改构造函数
func NewMyError(code int, msg, details, traceID string, cause error) *MyError {
    _, file, line, _ := runtime.Caller(1)
    return &MyError{
        Code:    code,
        Msg:     msg,
        Details: details,
        Time:    time.Now(),
        File:    file,
        Line:    line,
        TraceID: traceID,
        Cause:   cause,
    }
}

if err := someFunc(); err != nil {
    return NewMyError(3001, "operation failed", "cleanup failed", "req-67890", err)
}

errors.Is

errors.As

if errors.As(err, &myErr) {
    fmt.Println("Custom error code:", myErr.Code)
}