Fix possible panic in goroutine

Author: philippgille

consul.go

@@ -101,8 +101,10 @@ func watchConsulService(ctx context.Context, s servicer, tgt target, out chan<-
 		case ee := <-res:
 			out <- ee
 		case <-ctx.Done():
+			// Close quit so the goroutine returns and doesn't leak.
+			// Do NOT close res because that can lead to panics in the goroutine.
+			// res will be garbage collected at some point.
 			close(quit)
-			close(res)
 			return
 		}
 	}