lib/Request.js
function decrement(count) {
  count = count || 0;
  if (count <= MINUEND) {
    count = 0;
  } else {
    count -= MINUEND;
  }
  return count;
}
function decrement(count) {
  count = count || 0;
  if (count <= MINUEND) {
    count = 0;
  } else {
    count -= MINUEND;
  }
  return count;
}
释放1个请求