message: add the metaData example
diff: @@ -23,4 +23,14 @@ go(function () {
  var_dump($arr);
  });
  +
  +
  +go(function () {
  +
  + $pg = new Swoole\Coroutine\PostgreSql();
  + $conn = $pg -> connect ("host=127.0.0.1 port=5432 dbname=test user=wuzhenyu password=");
  + $metaData = $pg->metaData($conn, 'test');
  + var_dump($metaData);
  +
  +});
  ?>
  