From 7d7e34e753525618bc1c02646cb8ac981ed6f6c5 Mon Sep 17 00:00:00 2001
From: James Mills <prologic@shortcircuit.net.au>
Date: Tue, 5 Apr 2022 16:09:34 +1000
Subject: [PATCH] Fix panic updating metrics when not enabled

---
 msgbus.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/msgbus.go b/msgbus.go
index 124999d..1e5cee5 100644
--- a/msgbus.go
+++ b/msgbus.go
@@ -600,7 +600,9 @@ func (mb *MessageBus) Subscribe(id, topic string, opts ...SubscribeOption) chan
 				case ch <- msg:
 					n++
 				default:
-					mb.metrics.Counter("bus", "dropped").Inc()
+					if mb.metrics != nil {
+						mb.metrics.Counter("bus", "dropped").Inc()
+					}
 					return ErrBufferFull
 				}
 			}