Add example code, and improve the facing docs slightly.

cmd/discoverigd/discoverigd.go

@@ -1,36 +0,0 @@
-// Serves as a simple example/test of discovering UPnP devices on the local
-// network.
-package main
-
-import (
-	"fmt"
-
-	"github.com/huin/goupnp/dcps/internetgateway1"
-)
-
-func main() {
-	clients, errors, err := internetgateway1.NewWANPPPConnection1Clients()
-	if err != nil {
-		fmt.Println("Error discovering service with UPnP: ", err)
-		return
-	}
-
-	if len(errors) > 0 {
-		fmt.Printf("Error discovering %d services:\n", len(errors))
-		for _, err := range errors {
-			fmt.Println("  ", err)
-		}
-	}
-
-	fmt.Printf("Successfully discovered %d services:\n", len(clients))
-	for _, client := range clients {
-		device := &client.RootDevice.Device
-
-		fmt.Println("  Device:", device.FriendlyName)
-		if addr, err := client.GetExternalIPAddress(); err != nil {
-			fmt.Printf("    Failed to get external IP address: %v\n", err)
-		} else {
-			fmt.Printf("    External IP address: %v\n", addr)
-		}
-	}
-}