使用 http.Get() 时无效的内存地址或 nil 指针取消引用

Question

我刚开始学习 Go lang，我写了一个小演示，从 txt 中读取图片 url，将 url 放在一个数组中，然后将响应保存到一个文件中。

这是我的代码

package main

import (

"bufio"

"fmt"

"io"

"io/ioutil"

"net/http"

"os"

)

func main() {

fileName := "meinv.txt"

file, _ := os.Open(fileName)

picUrl := make([]string, 2000)

reader := bufio.NewReader(file)

for {

    line, _, err := reader.ReadLine()

    if err != io.EOF {

        fmt.Printf("file load %s \n", line)

        picUrl = append(picUrl, string(line))

    } else {

        file.Close()

        break

    }

}

fmt.Printf("file loaded,read to download \n")

fetchPic(picUrl)

}

func fetchPic(picUrl []string) {

var file string

for key, value := range picUrl {

    fmt.Printf("key is : %d,this line is %s \n\n", key, value)

    httpRequest, err := http.Get(string(value))

    fmt.Print("load ok \n")

    httpRequest.Body.Close()

    result, readErr := ioutil.ReadAll(httpRequest.Body)

    if readErr == nil {

        file = "pics/" + string(key) + ".jpg"

        ioutil.WriteFile(file, result, 0777)

        fmt.Print("Write ok \n")

    }

    len := len(string(result))

    fmt.Printf("length is %d", len)

    if err == nil {

        httpRequest = nil

        //result = nil

    } else {

        fmt.Print("load falt!!!!!!!!! \n")

    }

    defer httpRequest.Body.Close()

}

}

运行它，我得到了

key is : 0,this line is  

load ok 

panic: runtime error: invalid memory address or nil pointer dereference

[signal 0xb code=0x1 addr=0x40 pc=0x40123f]

goroutine 1 [running]:

runtime.panic(0x5f8300, 0x877688)

/usr/local/go/src/pkg/runtime/panic.c:266 +0xb6

main.fetchPic(0xc21239d000, 0x38be7, 0x4223c)

/home/lyn/www/goOnDev/fetch.go:40 +0x24f

main.main()

/home/lyn/www/goOnDev/fetch.go:28 +0x1b8

exit status 2

meinv.txt ，每个 url 一行 有人帮忙吗？谢谢