use extension_load to detect if swoole extension is installed

composer.json

@@ -15,7 +15,6 @@
     ],
     "require": {
         "php": "^7.1",
-        "ext-swoole": ">=1.9.3 || >=2.1.0",
         "illuminate/console": "~5.1",
         "illuminate/contracts": "~5.1",
         "illuminate/http": "~5.1",

src/Commands/HttpServerCommand.php

@@ -313,7 +313,9 @@ protected function isDaemon()
     protected function checkEnvironment()
     {
         if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
-            throw new \RuntimeException("Swoole extension doesn't support Windows OS yet");
+            throw new \RuntimeException("Swoole extension doesn't support Windows OS yet.");
+        } elseif (! extension_loaded('swoole')) {
+            throw new \RuntimeException("Can't detect Swoole extension installed.");
         }
     }
 }