Implement graceful shutdown for wakunode2 and chat2 (#490)

* Implement graceful shutdown

* Consistent use of QuitSuccess

examples/v2/chat2.nim

@@ -30,6 +30,7 @@ const Help = """
   help: Prints this help
   connect: dials a remote peer
   nick: change nickname for current chat session
+  exit: exits chat session
 """
 
 const
@@ -203,14 +204,11 @@ proc writeAndPrint(c: Chat) {.async.} =
       c.nick = await readNick(c.transp)
       echo "You are now known as " & c.nick
 
-#    elif line.startsWith("/exit"):
-#      if p.connected and p.conn.closed.not:
-#        await p.conn.close()
-#        p.connected = false
-#
-#      await p.switch.stop()
-#      echo "quitting..."
-#      quit(0)
+    elif line.startsWith("/exit"):
+     await c.node.stop()
+
+     echo "quitting..."
+     quit(QuitSuccess)
     else:
       # XXX connected state problematic
       if c.started:
@@ -368,6 +366,7 @@ proc processInput(rfd: AsyncFD, rng: ref BrHmacDrbgContext) {.async.} =
   node.subscribe(topic, handler)
 
   await chat.readWriteLoop()
+
   runForever()
   #await allFuturesThrowing(libp2pFuts)