A draft code to read a partial response from http server

partialResp.go

package main

import ("bufio"
        "fmt"
        "io"
        "net/http"
        "net"
        "strings")

type readFirstCloseSecond struct {
        r io.Reader
        c io.Closer
}

func (rfcs *readFirstCloseSecond) Read(b []byte) (int,error) {
        return rfcs.r.Read(b)
}

func (rfcs *readFirstCloseSecond) Close() error {
        return rfcs.c.Close()
}

func partialResp(u string) (*http.Response,error) {
        req,err := http.NewRequest("GET",u,nil)
        if err != nil {return nil,err}
        host := req.Host
        if ! strings.Contains(host,":") {
                host += ":80"
        }
        c,err := net.Dial("tcp",host)
        if err != nil {return nil,err}
        // Doesn't support proxy! Use req.WriteProxy to the proxy connection
        req.Write(c)
        resp,err := http.ReadResponse(bufio.NewReader(c),req)
        if err != nil {c.Close();return nil,err}
        resp.Body = &readFirstCloseSecond{resp.Body,c}
        return resp,err
}


func panicOnErr(err error) {
        if err != nil {
                panic(err.Error())
        }
}

func main() {
        u := "http://fuller.zen.co.uk/"+
                "test/100MB_nonzero.bin"
        resp,err := partialResp(u)
        panicOnErr(err)
        b := make([]byte,10)
        nr,err := resp.Body.Read(b)
        if nr != len(b) {
                println("read too little")
        } else {
                fmt.Println(b)
        }
        panicOnErr(err)
        resp.Body.Close()
}