Speed up reading HTTP response body for speed test - http

Question

I'm writing a (hopefully zero-dependency) speed test in Go leveraging Netflix's fast.com servers.
The code is pulling down several pieces of 25MB content, reading the response into a buffer and counting the bytes read along the way.
The code (speed test) works as expected on my development computer, but when I run it on a much tinier linux machine, the speed test caps out at measuring ~75Mbps (despite being hardwired into a network reliably providing 400+Mbps).
I believe the issue must be that because the machine is small, it's relatively slow at either reading the response or writing into the buffer.
I did a Go trace of the program on the 2 machines, and sure enough the Heap on the small linux machine continually gets full before GC clears it out; rinse and repeat.
The question is: what can I do about this to make my speed test accurate? More specifically, since I don't actually need the response data (because this is just a speed test), is there a way I can download and count the bytes from the HTTP response without actually bothering to write them anywhere, thus potentially saving time?
The relevant code is below. (Note: the reason I'm using http.NewRequest is because in some cases I build on URL params).
client := &http.Client{}
req, err := http.NewRequest("GET", url, nil)
resp, err := client.Do(req)
defer resp.Body.Close()
buffer := make([]byte, 128 * 1024)
for {
b, err := resp.Body.Read(buffer)
if err == io.EOF {
break
}
func() {
mu.Lock()
defer mu.Unlock()
*bytesRead += b
if *done {
return
}
}()
}
Edit: I should also add that the linux device has been tested and validated via other speed tests that it can achieve greater than 75Mbps.

Answer 1

You can use the io.Discard Writer in order to speedup the code, an example:
var bytesRead int64
client := &http.Client{}
req, err := http.NewRequest("GET", url, nil)
if err != nil {
panic(err)
}
resp, err := client.Do(req)
if err != nil {
panic(err)
}
defer resp.Body.Close()
nBytes, err := io.Copy(io.Discard, resp.Body)
if err != nil {
panic(err)
}
bytesRead += nBytes
By this way you don't need to iterate among a bytes buffer.