# Coroutine\PostgreSQL->connect 建立postgresql 非阻塞的协程连接 ```php function Coroutine\PostgreSQL->connect( string $connection_string); ``` example: ```php go(function () { $a = new Swoole\Coroutine\PostgreSQL(); $conn = $a -> connect ("host=127.0.0.1 port=5432 dbname=test user=wuzhenyu password="); var_dump($conn); }); ``` * 返回值：连接建立成功返回资源类型