title: regexp find for Chinese unicode character
body: <p>i have code like this </p>
  
  <pre><code>re, err = regexp.Compile(`\p{Han}*`)
  if err != nil {
      fmt.Println(err)
      return
  }
  s := "foo中文哦woqu"
  fmt.Println(re.FindString(s))
  </code></pre>
  
  <p>but it print empty.</p>
  
  <p>and then i change <code>\p{Han}*</code> to <code>\p{Han}+</code>, it display's 中文哦.</p>
  
  <p>change <code>\p{Han}*</code> to <code>\p{Han}?</code>, it print empty.</p>
  
  <p>I find the document like this:</p>
  
  <ul>
  <li>x*   zero or more x, prefer more </li>
  <li>x+   one or more x, prefer more </li>
  <li>x?   zero or one x, prefer one</li>
  </ul>
  
  <p>so i expect my print is:</p>
  
  <ul>
  <li><code>\p{Han}*</code> print 中文哦</li>
  <li><code>\p{Han}+</code> print 中文哦</li>
  <li><code>\p{Han}?</code> print 中</li>
  </ul>
  
  <p>could someone tell me what happened?</p>