Support php73 (#74)

* Support PHP 7.3

Co-authored-by: Deeka Wong <8337659+huangdijia@users.noreply.github.com>

src/Aspect/UdpSocketAspect.php

@@ -32,7 +32,7 @@ public function process(ProceedingJoinPoint $proceedingJoinPoint)
 
             /** @var string $chunk */
             $chunk = $proceedingJoinPoint->arguments['keys']['chunk'] ?? '';
-            [$ip, $port] = (fn () => [$this->ip, $this->port])->call($proceedingJoinPoint->getInstance());
+            [$ip, $port] = (function () { return [$this->ip, $this->port]; })->call($proceedingJoinPoint->getInstance());
 
             $socket = new Client(SWOOLE_SOCK_UDP);
             $socket->connect($ip, $port, 0.5);