From 20d65d4a761d9cb102286879c7fbb8e94d5d3f8e Mon Sep 17 00:00:00 2001
From: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Date: Mon, 6 Nov 2023 00:36:24 +0900
Subject: [PATCH] fix race condition in Close

---
 relay.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/relay.go b/relay.go
index 11aabc4..ea69eeb 100644
--- a/relay.go
+++ b/relay.go
@@ -39,6 +39,8 @@ func (s Status) String() string {
 }
 
 type Relay struct {
+	mu sync.Mutex
+
 	URL           string
 	RequestHeader http.Header // e.g. for origin header
 
@@ -553,6 +555,9 @@ func (r *Relay) Count(ctx context.Context, filters Filters, opts ...Subscription
 }
 
 func (r *Relay) Close() error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
 	if r.connectionContextCancel == nil {
 		return fmt.Errorf("relay not connected")
 	}