Fix potential races in createWaitForEvent*

It is possible (and noticed in the real world) that the goroutine might
enter the out select and then by the time get to writing to the channel
back for the event handling to have been canceled.

Author: mstoykov

common/helpers.go

@@ -144,16 +144,25 @@ func createWaitForEventHandler(
 				if stringSliceContains(events, ev.typ) {
 					if predicateFn != nil {
 						if predicateFn(ev.data) {
-							ch <- ev.data
+							select {
+							case ch <- ev.data:
+							case <-evCancelCtx.Done():
+								return
+							}
 						}
 					} else {
-						ch <- nil
+						select {
+						case ch <- nil:
+						case <-evCancelCtx.Done():
+							return
+						}
 					}
 					close(ch)
 
 					// We wait for one matching event only,
 					// then remove event handler by cancelling context and stopping goroutine.
 					evCancelFn()
+
 					return
 				}
 			}
@@ -185,9 +194,12 @@ func createWaitForEventPredicateHandler(
 			case ev := <-chEvHandler:
 				if stringSliceContains(events, ev.typ) &&
 					predicateFn != nil && predicateFn(ev.data) {
-					ch <- ev.data
-					close(ch)
-					evCancelFn()
+					select {
+					case ch <- ev.data:
+						close(ch)
+						evCancelFn()
+					case <-evCancelCtx.Done():
+					}
 					return
 				}
 			}