Implement session locking, unlocking

Send the LockSessions message and UnlockSessions message via DBus to
Systemd Logind to lock/unlock the current user's desktop.

.gitignore

@@ -0,0 +1 @@
+/session-lock-manager

session-lock-manager.go

@@ -3,6 +3,7 @@ package main
 import (
     "github.com/elvetemedve/session-lock-manager/device"
     "github.com/elvetemedve/session-lock-manager/authentication"
+    "github.com/elvetemedve/session-lock-manager/session"
     "github.com/jochenvg/go-udev"
     "os"
     "fmt"
@@ -12,13 +13,10 @@ func main() {
     serviceName := parseArguments()
     scanner := &device.UdevScanner{&udev.Udev{}}
     presence := &device.Presence{
-        authentication.AuthenticateCurrentUserAction(serviceName,
-            func(){
-                fmt.Println("Unlocking session.")
-            }, func(){}),
-        func(){
-            fmt.Println("Locking session.")
-        }}
+        authentication.AuthenticateCurrentUserAction(serviceName, session.Unlock, func(){
+                fmt.Fprintln(os.Stderr, "Authentication failed.")
+            }),
+        session.Lock}
     _, done := presence.Scan(os.Stdout, scanner)
     <-done
 }

session/manager.go

@@ -0,0 +1,42 @@
+package session
+
+import (
+    "log"
+    "fmt"
+    "github.com/godbus/dbus"
+)
+
+func Lock() {
+    error := callDbusMethod("LockSessions")
+	if error != nil {
+		fmt.Println(fmt.Sprintf("Failed to lock session: %s", error))
+        return
+	}
+
+    log.Println("Locking session.")
+}
+
+func Unlock() {
+    error := callDbusMethod("UnlockSessions")
+	if error != nil {
+		fmt.Println(fmt.Sprintf("Failed to lock session: %s", error))
+        return
+	}
+
+    log.Println("Unlocking session.")
+}
+
+func callDbusMethod(methodName string) (error) {
+    connection, error := dbus.SystemBus()
+	if error != nil {
+		fmt.Println(fmt.Sprintf("Failed to connectionect to session bus: %s", error))
+        return nil
+	}
+
+    object := connection.Object("org.freedesktop.login1", "/org/freedesktop/login1")
+    call := object.Call(fmt.Sprintf("org.freedesktop.login1.Manager.%s", methodName), 0)
+    if call.Err != nil {
+        return call.Err
+    }
+    return nil
+}