Read the IRC client's nick under its lock in the relay

After registration each IRC connection runs a second goroutine that sends
queued messages to the client, and it read c.nick without holding c.mu.
The goroutine that reads client commands changes c.nick under c.mu when
the client sends NICK, so the race detector failed
TestIntegrationTwoClients. Every read of c.nick in relay.go now takes
c.mu. No other field that goroutine reads changes after it starts.

Model: opus-5-5

internal/ircserver/relay.go

@@ -128,7 +128,11 @@ func (c *Conn) deliverIRCMessage(
 	default:
 		// Unknown command — deliver as server notice.
 		if text != "" {
-			c.sendFromServer("NOTICE", c.nick, text)
+			c.mu.Lock()
+			nick := c.nick
+			c.mu.Unlock()
+
+			c.sendFromServer("NOTICE", nick, text)
 		}
 	}
 }
@@ -158,8 +162,12 @@ func (c *Conn) deliverNumeric(
 		_ = json.Unmarshal(msg.Params, &params)
 	}
 
+	c.mu.Lock()
+	nick := c.nick
+	c.mu.Unlock()
+
 	allParams := make([]string, 0, 1+len(params)+1)
-	allParams = append(allParams, c.nick)
+	allParams = append(allParams, nick)
 	allParams = append(allParams, params...)
 
 	if text != "" {
@@ -177,8 +185,12 @@ func (c *Conn) deliverTextMessage(
 	from := msg.From
 	target := msg.To
 
+	c.mu.Lock()
+	nick := c.nick
+	c.mu.Unlock()
+
 	// Don't echo our own messages back.
-	if strings.EqualFold(from, c.nick) {
+	if strings.EqualFold(from, nick) {
 		return
 	}
 
@@ -192,9 +204,13 @@ func (c *Conn) deliverTextMessage(
 
 // deliverJoin sends a JOIN notification.
 func (c *Conn) deliverJoin(msg *db.IRCMessage) {
+	c.mu.Lock()
+	nick := c.nick
+	c.mu.Unlock()
+
 	// Don't echo our own JOINs (we already sent them
 	// during joinChannel).
-	if strings.EqualFold(msg.From, c.nick) {
+	if strings.EqualFold(msg.From, nick) {
 		return
 	}
 
@@ -206,7 +222,11 @@ func (c *Conn) deliverJoin(msg *db.IRCMessage) {
 
 // deliverPart sends a PART notification.
 func (c *Conn) deliverPart(msg *db.IRCMessage, text string) {
-	if strings.EqualFold(msg.From, c.nick) {
+	c.mu.Lock()
+	nick := c.nick
+	c.mu.Unlock()
+
+	if strings.EqualFold(msg.From, nick) {
 		return
 	}
 
@@ -227,7 +247,11 @@ func (c *Conn) deliverNickChange(
 	msg *db.IRCMessage,
 	newNick string,
 ) {
-	if strings.EqualFold(msg.From, c.nick) {
+	c.mu.Lock()
+	nick := c.nick
+	c.mu.Unlock()
+
+	if strings.EqualFold(msg.From, nick) {
 		return
 	}
 
@@ -241,7 +265,11 @@ func (c *Conn) deliverQuitMsg(
 	msg *db.IRCMessage,
 	text string,
 ) {
-	if strings.EqualFold(msg.From, c.nick) {
+	c.mu.Lock()
+	nick := c.nick
+	c.mu.Unlock()
+
+	if strings.EqualFold(msg.From, nick) {
 		return
 	}
 
@@ -302,7 +330,11 @@ func (c *Conn) deliverInviteMsg(
 	_ *db.IRCMessage,
 	text string,
 ) {
-	c.sendFromServer("NOTICE", c.nick, text)
+	c.mu.Lock()
+	nick := c.nick
+	c.mu.Unlock()
+
+	c.sendFromServer("NOTICE", nick, text)
 }
 
 // deliverMode sends a MODE change notification.

internal/server/server.go

@@ -71,7 +71,14 @@ func New(
 	lifecycle.Append(fx.Hook{
 		OnStart: func(_ context.Context) error {
 			srv.startupTime = time.Now()
-			go srv.Run() //nolint:contextcheck
+
+			// Build the router before OnStart returns, so srv can
+			// handle requests as soon as the app has started.
+			srv.configure()
+			srv.enableSentry()
+			srv.SetupRoutes()
+
+			go srv.serve() //nolint:contextcheck
 
 			return nil
 		},
@@ -83,13 +90,6 @@ func New(
 	return srv, nil
 }
 
-// Run starts the server configuration, Sentry, and begins serving.
-func (srv *Server) Run() {
-	srv.configure()
-	srv.enableSentry()
-	srv.serve()
-}
-
 // ServeHTTP delegates to the chi router.
 func (srv *Server) ServeHTTP(
 	writer http.ResponseWriter,
@@ -202,8 +202,6 @@ func (srv *Server) serveUntilShutdown() {
 		Handler:        srv,
 	}
 
-	srv.SetupRoutes()
-
 	srv.log.Info(
 		"http begin listen", "listenaddr", listenAddr,
 	)