ioutil.ReadAll惨败

Question

I'm trying to get an io.Reader back from this weather it's a link or a path I'm given. For some context I'm using flags

func getString(link, path string) (io.Reader, error) {

    var dick io.ReadWriter

    if link != "" {
        resp, err := http.Get(link)
        if err != nil {
            return nil, err
        }

        io.Copy(dick, resp.Body)
    }

    if path != "" {
        file, err := os.Open(path)
        if err != nil {
            return nil, err
        }

        io.Copy(dick, file)
    }

    return dick, nil

}

and boom

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x46e949]

this bad boy comes along

Answer 1

io.ReadWriter is an interface, what you need is an instance of io.ReadWriter to write into (via io.Copy) and return the io.Reader interface off of that.

One type that comes to mind is a bytes.Buffer. Your code would look like this

func getString(link, path string) (io.Reader, error) {

    dick := bytes.NewBuffer(nil)

    if link != "" {
        resp, err := http.Get(link)
        if err != nil {
            return nil, err
        }

        io.Copy(dick, resp.Body)
    }

    if path != "" {
        file, err := os.Open(path)
        if err != nil {
            return nil, err
        }

        io.Copy(dick, file)
    }

    return dick, nil

}

You are also swallowing the error from io.Copy which isn't a great idea.