examples: Add asynchronous D-Bus client example

Extend the server example with a Sleep method and add a client to
demonstrate an asynchronous D-Bus call with possible timeout handling.

_examples/server.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	"time"
 
 	"github.com/godbus/dbus/v5"
 	"github.com/godbus/dbus/v5/introspect"
@@ -14,6 +15,9 @@ const intro = `
 		<method name="Foo">
 			<arg direction="out" type="s"/>
 		</method>
+		<method name="Sleep">
+			<arg direction="in" type="u"/>
+		</method>
 	</interface>` + introspect.IntrospectDataString + `</node> `
 
 type foo string
@@ -23,6 +27,12 @@ func (f foo) Foo() (string, *dbus.Error) {
 	return string(f), nil
 }
 
+func (f foo) Sleep(seconds uint) *dbus.Error {
+	fmt.Println("Sleeping", seconds, "second(s)")
+	time.Sleep(time.Duration(seconds) * time.Second)
+	return nil
+}
+
 func main() {
 	conn, err := dbus.ConnectSessionBus()
 	if err != nil {

_examples/timeout.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/godbus/dbus/v5"
+)
+
+func main() {
+	conn, err := dbus.ConnectSessionBus()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Failed to connect to session bus:", err)
+		os.Exit(1)
+	}
+	defer conn.Close()
+
+	ch := make(chan *dbus.Call, 10)
+
+	obj := conn.Object("com.github.guelfey.Demo", "/com/github/guelfey/Demo")
+	obj.Go("com.github.guelfey.Demo.Sleep", 0, ch, 5) // 5 seconds
+
+	nrAttempts := 3
+	isResponseReceived := false
+
+	for i := 1; i <= nrAttempts && !isResponseReceived; i++ {
+		fmt.Println("Waiting for response, attempt", i)
+
+		select {
+		case call := <-ch:
+			if call.Err != nil {
+				fmt.Fprintln(os.Stderr, "Failed to call Sleep method:", err)
+				os.Exit(1)
+			}
+			isResponseReceived = true
+			break
+
+		// Handle timeout here
+		case <-time.After(2 * time.Second):
+			fmt.Println("Timeout")
+			break
+		}
+	}
+
+	if isResponseReceived {
+		fmt.Println("Done!")
+	} else {
+		fmt.Fprintln(os.Stderr, "Timeout waiting for Sleep response")
+	}
+}