node series/q.js 的结果，有时不是顺序的。

[rhinoceros]

localhost:node-demo rock$ node series/q.js 
remove user
remove posts
remove comments
remove ok
localhost:node-demo rock$ node series/q.js 
remove user
remove posts
remove comments
remove ok


# 看这儿
localhost:node-demo rock$ node series/q.js 
remove user
remove ok
remove posts
remove comments




localhost:node-demo rock$ node series/q.js 
remove user
remove posts
remove comments
remove ok
localhost:node-demo rock$ node series/q.js 
remove user
remove posts
remove comments
remove ok

localhost:node-demo rock$ node -v
v10.10.0
localhost:node-demo rock$ npm version
{ callback_hell: '0.0.0',
  npm: '6.4.1',
  ares: '1.14.0',
  cldr: '33.1',
  http_parser: '2.8.0',
  icu: '62.1',
  modules: '64',
  napi: '3',
  nghttp2: '1.33.0',
  node: '10.10.0',
  openssl: '1.1.0i',
  tz: '2018e',
  unicode: '11.0',
  uv: '1.23.0',
  v8: '6.8.275.30-node.24',
  zlib: '1.2.11' }