message: update examples of postgresql
diff: @@ -6,10 +6,8 @@ go(function () {
  $pg = new Swoole\Coroutine\PostgreSql();
  $conn = $pg -> connect ("host=127.0.0.1 port=5432 dbname=test user=wuzhenyu password=");
  $result = $pg->query($conn, 'SELECT * FROM test;');
  - $arr = $pg->fetchAll($result);// the same with affectedRows(),fetchObject(),fetchAssoc(),fetchArray(),fetchRow()
  + $arr = $pg->fetchAll($result);// the same with affectedRows(),fetchObject(),fetchAssoc(),fetchArray(),fetchRow(),numRows()
  var_dump($arr);
  - //$numRows = $pg->numRows($result);
  - //var_dump($numRows);
  });
  