How to call web service and stop VPN server in applicationWillTerminate Method?

I have implemented VPN Server logic (NETunnelProviderManager) and start tunnel on NETunnelProviderSession using startTunnel(options: ["ipv4": dnsIpv4]) method. VPN Working fine and started properly. I want to stop VPN tunnel in applicationWillTerminate(_ application: UIApplication) method when application terminating. I have also put code logic for that but it will not stop VPN And I also want to call API (Web-service) when application going to terminate.

func applicationWillTerminate(_ application: UIApplication){

//Stop VPN

self.vpnService.disable { (error) in

}

//Perform API Calling

self.myAPI()

}