golang http Concurrent Requests post eof

I'm running a small client in Go We're getting a number of false alarms at the moment, which seem to come down to client.Do() returning an EOF error when num>=1000

This is the essence of my code:

func DoCreate(js string) {

url2 := "http://ift.tt/1C2gLOE"

client := &http.Client{
    CheckRedirect: nil,
}

postBytesReader := bytes.NewReader([]byte(js))
request, _ := http.NewRequest("POST", url2, postBytesReader)

resp, err := client.Do(request)
if err != nil {
    fmt.Println(err)  // Post http://ift.tt/1C2gLOE: EOF
    return
}
body, _:= ioutil.ReadAll(resp.Body)
fmt.Println(string(body))

defer resp.Body.Close()

}

func main() {

    for i := 0; i < num; i++ {
        var pq CreateReqInfo
        pq.Uid = strconv.Itoa(bid + i)
        petstr, _ := json.Marshal(pq)
        go DoCreate(string(petstr))
    }

}

the problem about number of file handles or max connections?