定義測試介面  testInterface/mock/main.go

package mock

type Retriever struct {
    Contents string
}

// 給結構體新增方法
func (r Retriever) Get(url string) string {
    return r.Contents
}

定義真實介面 testInterface/real/main.go

package real

import (
    "net/http"
    "net/http/httputil"
    "time"
)

type Retriever struct
 
 {
    UserAgent string
    TimeOut time.Duration
}

func (r Retriever) Get(url string) string  {
    res,err := http.Get(url)
    if err != nil {
        panic(err)
    }

    result,err := httputil.DumpResponse(res,true)
    if err != nil {
        panic(err)
    }

    // 讀完 Response 的 body 後需要關掉
    res.Body.Close()

    
 
return string(result)
}

正常使用 main.go

package main

import (
    "fmt"
    "testInterface/mock"
    "testInterface/real"
)

// 定義介面
type Retriver interface {
    Get(url string) string
}

// 定義方法，呼叫介面
func download(r Retriver) string {
    return r.Get("https://baidu.com")
}

func main() {
    var r Retriver

    r 
 
= mock.Retriever{Contents: "this is a mock"}
    fmt.Println(download(r))

    var newR Retriver
    newR = real.Retriever{}
    fmt.Println(download(newR))

}