Remove global API for settings engine

Limit global API to the basics needed to construct a PeerConnection.

examples/data-channels-detach-create/main.go

@@ -14,9 +14,15 @@ const messageSize = 15
 
 func main() {
 	// Since this behavior diverges from the WebRTC API it has to be
-	// enabled using global switch.
-	// Mixing both behaviors is not supported.
-	webrtc.DetachDataChannels()
+	// enabled using a settings engine. Mixing both detached and the
+	// OnMessage DataChannel API is not supported.
+
+	// Create a SettingEngine and enable Detach
+	s := webrtc.SettingEngine{}
+	s.DetachDataChannels()
+
+	// Create an API object with the engine
+	api := webrtc.NewAPI(webrtc.WithSettingEngine(s))
 
 	// Everything below is the pion-WebRTC API! Thanks for using it ❤️.
 
@@ -29,8 +35,8 @@ func main() {
 		},
 	}
 
-	// Create a new RTCPeerConnection
-	peerConnection, err := webrtc.NewPeerConnection(config)
+	// Create a new RTCPeerConnection using the API object
+	peerConnection, err := api.NewPeerConnection(config)
 	if err != nil {
 		panic(err)
 	}
@@ -81,7 +87,7 @@ func main() {
 
 	// Wait for the answer to be pasted
 	answer := webrtc.SessionDescription{}
-	signal.Decode(signal.MustReadStdin(), answer)
+	signal.Decode(signal.MustReadStdin(), &answer)
 
 	// Apply the answer as the remote description
 	err = peerConnection.SetRemoteDescription(answer)