docs: function copyFile(src, dist, callback) {
      let rs = fs.createReadStream(src),
          ws = fs.createWriteStream(dist);
  
      // 监听事件
      rs.on('error', callback);
      ws.on('error', callback);
      ws.on('close', callback);
  
      // 传输文件
      rs.pipe(ws);
  }