Go lang error interface

gistfile1.go

package main

import (
    "fmt"
    "time"
)

type MyError struct {
    When time.Time
    What string
}

// 接口实现
func (e *MyError) Error() string {
    return fmt.Sprintf("at %v, %s",
        e.When, e.What)
}

// error是内置接口，当然也是一个type
func run(tag int) (error, string) {
    if tag == 0 {
        
    	return &MyError{
        	time.Now(),
        	"it didn't work",
    	}, "ERROR"
    } else {
        return nil, "SUCCESS" 
    }
}

func main() {
    if err, msg := run(1); err != nil {
        
        fmt.Println(err, msg)
    } else {
        fmt.Println(msg)
    }
}