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 mainimport ("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 stringfor 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 +0xb6main.fetchPic(0xc21239d000, 0x38be7, 0x4223c)/home/lyn/www/goOnDev/fetch.go:40 +0x24fmain.main()/home/lyn/www/goOnDev/fetch.go:28 +0x1b8exit status 2meinv.txt ，每个 url 一行 有人帮忙吗？谢谢