如何在Golang中构建错误链_Golang error wrapping应用场景

if err != nil {
    return fmt.Errorf("failed to read config: %w", err)
}

if errors.Is(err, os.ErrNotExist) {
    log.Println("file does not exist")
}

var pathErr *os.PathError
if errors.As(err, &pathErr) {
    log.Printf("path error occurred on path: %s", pathErr.Path)
}

func loadConfig() error {
    _, err := os.Open("/path/to/config.json")
    if err != nil {
        return fmt.Errorf("config load failed: %w", err)
    }
    return nil
}

func connectDB() error {
    err := loadConfig()
    if err != nil {
        return fmt.Errorf("database connect failed: %w", err)
    }
    // ... connect logic
    return nil
}

func createUser(name string) error {
    err := connectDB()
    if err != nil {
        return fmt.Errorf("create user %q failed: %w", name, err)
    }
    return nil
}

type MyError struct {
    Msg  string
    Err  error
    Time time.Time
}

func (e *MyError) Error() string {
    return fmt.Sprintf("%s: %v", e.Msg, e.Err)
}

func (e *MyError) Unwrap() error {
    return e.Err
}

return &MyError{
    Msg: "custom operation failed",
    Err: fmt.Errorf("inner failure: %w", origErr),
    Time: time.Now(),
}