From 58741aa877bcb591c8e0e68b083d04d7c673a4b5 Mon Sep 17 00:00:00 2001
From: Oleksandr Ohurtsov <iscander@gmail.com>
Date: Mon, 5 Jul 2021 13:44:36 +0300
Subject: [PATCH] Fix datarace while update a channel.lastEventID

Protect the option by wrappring into a mutex. The datarace is gone.
It closes https://github.com/alexandrevicenzi/go-sse/issues/18
---
 channel.go  | 2 ++
 sse_test.go | 5 +++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/channel.go b/channel.go
index 82be419..c66f948 100644
--- a/channel.go
+++ b/channel.go
@@ -23,7 +23,9 @@ func newChannel(name string) *Channel {
 
 // SendMessage broadcast a message to all clients in a channel.
 func (c *Channel) SendMessage(message *Message) {
+	c.mu.Lock()
 	c.lastEventID = message.id
+	c.mu.Unlock()
 
 	c.mu.RLock()
 
diff --git a/sse_test.go b/sse_test.go
index e632ca6..63634fc 100644
--- a/sse_test.go
+++ b/sse_test.go
@@ -90,8 +90,9 @@ func TestServer(t *testing.T) {
 }
 
 func TestMultipleTopics(t *testing.T) {
-	// usage pattern we have a client which subsribed to multiple channels
-	// in one connection
+	// The usage pattern: Imagine  we have a client which subsribed to multiple topics
+	// inside a connection. It track changes of specific items state by their ID
+	// for example.
 	sendersWg := sync.WaitGroup{}
 	workerWg := sync.WaitGroup{}
 	m := sync.Mutex{}