Update shared-mutable-state-and-concurrency.md
Main func should return Unit, otherwise it won't run
diff --git a/docs/shared-mutable-state-and-concurrency.md b/docs/shared-mutable-state-and-concurrency.md
index 48d3d70..30d7334 100644
--- a/docs/shared-mutable-state-and-concurrency.md
+++ b/docs/shared-mutable-state-and-concurrency.md
@@ -501,7 +501,7 @@
}
//sampleStart
-fun main() = runBlocking {
+fun main() = runBlocking<Unit> {
val counter = counterActor() // create the actor
withContext(Dispatchers.Default) {
massiveRun {