Add a balancer example to README.md.

Author: yruslan

README.md

@@ -338,6 +338,38 @@ Int received: 2
 String received: edef
 ```
 
+### A balancer example
+Here is example function that balances inputs from two channels into two output channels.
+Notice that `select()` is used to wait for any of the channels to have an incoming message, as well as
+to select a free output channel. You can mix `sender()` and `recver()` calls in the same `select()` statement.
+A finish channel is used to signal the end of the balancing process.
+
+```scala
+def balancer(input1: ReadChannel[Int],
+             input2: ReadChannel[Int],
+             output1: WriteChannel[Int],
+             output2: WriteChannel[Int],
+             finishChannel: ReadChannel[Boolean]): Unit = {
+  var v: Int = 0
+  var exit = false
+
+  while (!exit) {
+    select(
+      input1.recver(x => v = x),
+      input2.recver(x => v = x),
+      finishChannel.recver(_ => exit = true)
+    )
+
+    if (!exit) {
+      select(
+        output1.sender(v) {},
+        output2.sender(v) {}
+      )
+    }
+  }
+}
+```
+
 ### Scala-specific channel features
 Since Scala is a functional language, this implementation of channels supports functional operations used in for comprehension.
 

src/test/scala/com/github/yruslan/channel/GuaranteesSuite.scala

@@ -125,7 +125,11 @@ class GuaranteesSuite extends AnyWordSpec {
                            out2: com.github.yruslan.channel.Channel[Int]): Unit = {
     val results = new ListBuffer[(Int, Int)]
 
-    def balancer(input1: ReadChannel[Int], input2: ReadChannel[Int], output1: WriteChannel[Int], output2: WriteChannel[Int], finishChannel: ReadChannel[Boolean]): Unit = {
+    def balancer(input1: ReadChannel[Int],
+                 input2: ReadChannel[Int],
+                 output1: WriteChannel[Int],
+                 output2: WriteChannel[Int],
+                 finishChannel: ReadChannel[Boolean]): Unit = {
       var v: Int = 0
       var exit = false