fix the sample code

README.md

@@ -29,25 +29,27 @@ val bootstrap = Kafka.newRichClient("[host]:[port]")
 
 // create a client for the leader of specific topic partition
 val metadata = bootstrap.metadata("topic")
-val client = for {
-  metadata <- metadata
-  leader <- Future.value(metadata.head.partitions(0).leader.get)
-  client <- Future.value(Kafka.newRichClient(s"${leader.host}:${leader.port}"))
-} yield client
-
-// get offset
-val offset = client.map(_.offset("topic", 0, -1).get.offsets(0)).get
-
-// produce a message
-client.foreach(_.produce("topic", 0, "foobar"))
-
-// fetch messages
-val msgs = client.flatMap {
-  _.fetch("topic", 0, offset).map {
-    _.messages.map(_.message.value.toString("UTF-8"))
+val client = metadata.map {
+  _.head.partitions(0).leader.map { l =>
+    Kafka.newRichClient(s"${l.host}:${l.port}")
+  }.get
+}
+
+client.foreach { cli =>
+  // get offset
+  val offset = cli.offset("topic", 0, -1).map(_.offsets(0))
+
+  // produce a message
+  val produced = offset.unit before cli.produce("topic", 0, "foobar").unit
+
+  // fetch messages
+  val msgs = produced before offset.flatMap { offset =>
+    cli.fetch("topic", 0, offset).map {
+      _.messages.map(_.message.value.toString("UTF-8"))
+    }
   }
+  msgs.foreach(_.foreach(println))
 }
-msgs.foreach(_.foreach(println))
 ```
 
 ## Build