为什么HTTP流服务器无法成功发送线路？

Question

I have a very basic http server and http client. The server is not sending out the data when chunked despite flushing it. I have validated both with a go http client and curl.

Here is the server:

func main() { 
    r := mux.NewRouter()
    baseURL := ""
    r.HandleFunc(baseURL+"/",handler).Methods("GET")
    listener, _ := net.Listen("tcp", "127.0.0.1:0")
    http.Handle("/",r)
    go http.Serve(listener,nil)
    url = "http://" + listener.Addr().String() + "/"
    fmt.Println(url)
    TestSend()
}

func writeHeaders(w http.ResponseWriter, code int) {
    w.Header().Set("Content-Type", "text/plain")
    w.WriteHeader(code)
}

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Println("handler")
    writeHeaders(w, 200)
    rsc := bufio.NewScanner(strings.NewReader(response))
    for rsc.Scan() {
        sender <- rsc.Text()
    }
    for d := range sender {
        w.Write([]byte(d))
        w.(http.Flusher).Flush()
        fmt.Println("wrote and flushed "+d)
    }
}

And the client:

res, _ := http.Get(url)
reader := bufio.NewReader(res.Body)
for {
    fmt.Println("ReadBytes")
    data, err := reader.ReadBytes('')
    fmt.Println("read")
    if err != nil {
        fmt.Println("error!")
        fmt.Println(err)
        return
    }
    fmt.Println("read line "+string(data))
}

I get the server saying it is sending and flushing, and I get the "ReadBytes" saying it is waiting to read, but it never reads any lines:

$ go run httptest.go
http://127.0.0.1:55967/
handler
wrote and flushed abc
wrote and flushed def
wrote and flushed ghi
wrote and flushed jkl
wrote and flushed mno
ReadBytes
(here it just waits)

If, while it is running, I curl, I get the right headers, but no data:

$ curl -i http://127.0.0.1:55957/
HTTP/1.1 200 OK
Content-Type: text/plain
Date: Sun, 02 Aug 2015 07:01:21 GMT
Transfer-Encoding: chunked


(no data here at all)

Clearly the data is not leaving the server, but why? I am Flushing it.