将图像从html表单传递到Go

Question

I have a html page that has the follow code.

<form action="/image" method="post"
enctype="multipart/form-data">
<label for="file">Filename:</label>
<input type="file" name="file" id="file"><br>
<input type="submit" name="submit" value="Submit">
</form>

I then have some Go code to get the file on the back end.

func uploaderHandler(w http.ResponseWriter, r *http.Request) {

   userInput := r.FormValue("file")

but anytime I try to use userInput from the go script, it returns nothing. Am I passing the variables wrong?

EDIT: I know how to upload things to golang that are text/passwords. I am having trouble uploading images to Go with the code.

EDIT 2: Read the Go guide a found the solution. See below.

Answer 1

First you need to use req.FormFile not FormValue, then you will have to manually save the image to a file.

Something like this:

func HandleUpload(w http.ResponseWriter, req *http.Request) {
    in, header, err := req.FormFile("file")
    if err != nil {
        //handle error
    }
    defer in.Close()
    //you probably want to make sure header.Filename is unique and 
    // use filepath.Join to put it somewhere else.
    out, err := os.OpenFile(header.Filename, os.O_WRONLY, 0644)
    if err != nil {
        //handle error
    }
    defer out.Close()
    io.Copy(out, in)
    //do other stuff
}