http.ReadRequest后的Body字段为空，请大家帮忙

package main

import (
    "bufio"
    "bytes"
    "fmt"
    "io"
    "io/ioutil"
    "net/http"
)

func ParseReq(b []byte) (*http.Request, error) {
    // func ReadRequest(b *bufio.Reader) (req *Request, err error) { return readRequest(b, deleteHostHeader) }
    var buf io.ReadWriter
    buf = new(bytes.Buffer)
    buf.Write(b)
    bufr := bufio.NewReader(buf)
    return http.ReadRequest(bufr)
}

func main() {
    context := []byte(
        `POST http://www.hh.com/login HTTP/1.1
Accept: */*
Connection: Keep-Alive
Content-Type: application/x-www-form-urlencoded
User-Agent: curl/7.47.0

name=bao`)

    req, err := ParseReq(context)
    if err != nil {
        fmt.Println("parse error, ", err)
    }
    fmt.Printf("req:---->%#v\n", req)
    if req.Method == "POST" {
        fmt.Println("URLEncoded form")
        body, err := ioutil.ReadAll(req.Body)
        if err != nil {
            fmt.Println("readall error， ", err)
        }
        fmt.Println(string(body)) //why empty?
        // err := req.ParseForm()
    }
}

输出结果

req:---->&http.Request{Method:"POST", URL:(*url.URL)(0xc82007a080), Proto:"HTTP/1.1", ProtoMajor:1, ProtoMinor:1, Header:http.Header{"Accept":[]string{"*/*"}, "Connection":[]string{"Keep-Alive"}, "Content-Type":[]string{"application/x-www-form-urlencoded"}, "User-Agent":[]string{"curl/7.47.0"}}, Body:(*struct { http.eofReaderWithWriteTo; io.Closer })(0x91fbb0), ContentLength:0, TransferEncoding:[]string(nil), Close:false, Host:"www.hh.com", Form:url.Values(nil), PostForm:url.Values(nil), MultipartForm:(*multipart.Form)(nil), Trailer:http.Header(nil), RemoteAddr:"", RequestURI:"http://www.hh.com/login", TLS:(*tls.ConnectionState)(nil), Cancel:(<-chan struct {})(nil)}
URLEncoded form

不知道为何body为空，看了源码也不清楚，没看懂源码的Body是怎么赋值的