reduced chance of mutex related panic

.gitignore

@@ -24,7 +24,7 @@ profile.cov
 # Go workspace file
 go.work
 go.work.sum
-
+stresser.go
 # env file
 .env
 

main.go

@@ -777,8 +777,7 @@ func joinChannel(c *Client, name string) {
 	// reject duplicate join
 	if _, exists := ch.members[c.nick]; exists {
 		ch.mu.Unlock()
-		c.fwrite(":server 443 %s %s %s :is already on channel\r\n",
-			c.nick, c.nick, name)
+		c.fwrite(":server 443 %s %s %s :is already on channel\r\n", c.nick, c.nick, name)
 		return
 	}
 	// clean up stale empty nick
@@ -788,28 +787,26 @@ func joinChannel(c *Client, name string) {
 	c.channels[name] = ch
 	ch.mu.Unlock()
 
-	// echo JOIN to client
 	fmt.Fprintf(c.conn, ":%s JOIN %s\r\n", c.nick, name)
-	// broadcast JOIN to others
-	for _, member := range ch.members {
+	ch.mu.RLock()
+	members := make([]*Client, 0, len(ch.members))
+	for _, m := range ch.members {
+		members = append(members, m)
+	}
+	ch.mu.RUnlock()
+	for _, member := range members {
 		if member != c {
 			fmt.Fprintf(member.conn, ":%s JOIN %s\r\n", c.nick, name)
 		}
 	}
-
-	// topic
 	if ch.description != "" {
 		c.fwrite(":server 332 %s %s :%s\r\n", c.nick, name, ch.description)
 	} else {
 		c.fwrite(":server 331 %s %s :No topic is set\r\n", c.nick, name)
 	}
-
-	// names list
 	c.sendNames(ch)
-
-	// MODE if op
 	if ch.ops[c.nick] {
-		for _, member := range ch.members {
+		for _, member := range members {
 			member.fwrite(":server MODE %s +o %s\r\n", name, c.nick)
 		}
 	}
@@ -831,7 +828,7 @@ func (c *Client) partChannel(name string) {
 		fmt.Fprintf(member.conn, ":%s PART %s\r\n", c.nick, name)
 	}
 	ch.mu.Unlock()
-	broadcastNames(ch)
+	//broadcastNames(ch)
 }
 func addChannel(name string, description string) {
 	name = normalizeChannelName(name)
@@ -899,7 +896,7 @@ func (c *Client) checkRegistration() {
 		} else {
 			c.fwrite("%s :MOTD File is missing", c.nick)
 		}
-		fmt.Fprintf(c.conn, ":server 376 %s :End of MOTD\r\n", c.nick)
+		c.fwrite(":server 376 %s :End of MOTD\r\n", c.nick)
 	}
 }
 func reloadMOTD() {
@@ -943,7 +940,7 @@ func showWho(c *Client, name string) {
 	for _, member := range ch.members {
 		c.fwrite(":server 352 %s %s %s server %s H :0 %s\r\n", c.nick, name, member.host, member.nick, member.nick)
 	}
-	fmt.Fprintf(c.conn, ":server 315 %s %s :End of WHO list\r\n", c.nick, name)
+	c.fwrite(":server 315 %s %s :End of WHO list\r\n", c.nick, name)
 }
 func (c *Client) handleList() {
 	chMu.Lock()
@@ -1017,18 +1014,30 @@ func (c *Client) cleanup() {
 		ch.mu.Lock()
 		delete(ch.members, c.nick)
 		ch.mu.Unlock()
-		for nick, member := range ch.members {
-			if nick != c.nick {
+		ch.mu.RLock()
+		snapshot := make([]*Client, 0, len(ch.members))
+		for _, member := range ch.members {
+			snapshot = append(snapshot, member)
+		}
+		ch.mu.RUnlock()
+		for _, member := range snapshot {
+			if member.nick != c.nick {
 				member.fwrite(":%s PART %s\r\n", c.nick, name)
 			}
 		}
+
 		delete(c.channels, name)
 	}
 	cliMu.RLock()
+	snapshot := make([]*Client, 0, len(clients))
 	for _, other := range clients {
-		other.fwrite(":%s QUIT :Client disconnected\r\n", c.nick)
+		snapshot = append(snapshot, other)
 	}
 	cliMu.RUnlock()
+
+	for _, other := range snapshot {
+		other.fwrite(":%s QUIT :Client disconnected\r\n", c.nick)
+	}
 }
 
 func broadcastNames(ch *Channel) {