以字符串形式发送带有请求正文的POST请求

Question

I have a page setup on my webserver with an 'email address' box and a submit button. I have it so when it is submitted, it sends a post request to check if it exists in my database. I have been using Go to try and send this POST request. However, I need to send the request body as the following:

demo_mail=<email>

I haven't found anything remotely useful online, only posts asking how to send the data with JSON rather than a string. I currently have the following code which runs but fails to send the POST request with the post data above.

req, err := http.NewRequest("POST", "<MY PAGE>", ioutil.NopCloser(bytes.NewBufferString("demo_mail=" + email)))
            req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
            req.Header.Set("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8")
            req.Header.Set("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.80 Safari/537.36")



            resp, err := client.Do(req)
            if err != nil {
                 color.Red("Error.")
            }
            defer resp.Body.Close()

            body, _ := ioutil.ReadAll(resp.Body)


            if strings.Contains(string(body), "Success") {
                fmt.Println("Email exists")
            } else {
                fmt.Println("Fail")
            }

Any help is appreciated.

Answer 1

The body you expect is actually correctly sent but maybe not in the way you want:

POST /foo HTTP/1.1
...
Transfer-Encoding: chunked
...
Content-Type: application/x-www-form-urlencoded
...

17
demo_mail=<[e-mail]>
0

Since you've wrapped your string into a io.NopCloser it will assume that the length is not known up-front. It will therefore use chunked transfer encoding to send each chunk returned from the io.Reader prefixed by its length and once everything done the final chunk with length 0.

If you don't want to have this behavior you need to provide a buffer where the length is known up-front. This can be done by simply removing the ioutil.NopCloser around the bytes.NewBufferString:

req, err := http.NewRequest("POST", "<MY PAGE>", bytes.NewBufferString("demo_mail=" + email))

With this the request will use Content-length instead of chunked transfer encoding and the body will only contain the string:

POST /foo HTTP/1.1
...
Content-Length: 23
...
Content-Type: application/x-www-form-urlencoded
...

demo_mail=<[e-mail]>