code: func ThrottledReader(r io.Reader, bytesPerSec int, maxBurst time.Duration) ThrottlerReader {
  	return &throttledReader{
  		wrap:    r,
  		limiter: newRateLimiter(bytesPerSec, maxBurst),
  	}
  }
docs: // ThrottledReader ensures that reads to `r` never exceeds a specified rate of
  // bytes per second. The `maxBurst` duration changes how often the verification is
  // done. The smaller the value, the less bursty, but also the more overhead there
  // is to the throttling.