Add sync.WaitGroup to the payloads buffer test

In order to prevent payloads buffer tests fail intermitently
added syncronization to make sure assertion won't happen before
message appears in the channel.

Change-Id: I141492f87c58cbcecb82b8aa21feafce3da83785
Signed-off-by: Artem Barger <[email protected]>

Author: C0rWin

gossip/state/payloads_buffer_test.go

@@ -145,11 +145,13 @@ func TestPayloadsBufferImpl_ConcurrentPush(t *testing.T) {
 	var errors []error
 
 	ready := int32(0)
+	readyWG := sync.WaitGroup{}
+	readyWG.Add(1)
 	go func() {
-
 		// Wait for next expected block to arrive
 		<-buffer.Ready()
 		atomic.AddInt32(&ready, 1)
+		readyWG.Done()
 	}()
 
 	for i := 0; i < concurrency; i++ {
@@ -171,6 +173,7 @@ func TestPayloadsBufferImpl_ConcurrentPush(t *testing.T) {
 		}
 	}
 
+	readyWG.Wait()
 	assert.Equal(t, int32(1), atomic.LoadInt32(&ready))
 	assert.Equal(t, 1, success)
 	// Buffer size has to be only one