Why does request.ParseForm() drain the request.Body?

In this code, if I comment the ParseForm() invocation the request works as expected

package main

import (
	"fmt"
	"net/http"
	"net/url"
	"strings"
)

func main() {

	v := make(url.Values)
	v.Set("status", "yeah!")
	request, error := http.NewRequest("POST", "http://httpbin.org/post", strings.NewReader(v.Encode()))
	if error != nil {
		fmt.Println(error)
	}

	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	err:=request.ParseForm()
	if err != nil {
		fmt.Println(err)	
	}
	fmt.Println(request.Form["status"])

	response, error := http.DefaultClient.Do(request)
	if error != nil {
		fmt.Println(error)
	} else {
		fmt.Println(response)
	}
}

But if I call ParseForm() the body is cleared and I get:

Post http://httpbin.org/post: http: Request.ContentLength=14 with Body length 0

Is like the Body length has been drained. How can I access the form values? I need to create a signature of the request. Is there other way (other than creating the signature directly from the parameters directly? )

Use ParseForm for read the request, not set.
For simple POST you can do:

resp, err := http.PostForm("http://example.com/form", url.Values{"key": {"Value"}, "id": {"123"}})

http://golang.org/pkg/net/http/#Post
http://golang.org/pkg/net/http/#PostForm