fix(tm2/pkg/bft/node): make Node.startRPC not leak listeners on any e…

…rror

Once Node.startRPC encounters an error, previously it was discarding
all the created listeners and leaking them unclosed. This change fixes
that using Go's named return values.

Fixes gnolang#3639

tm2/pkg/bft/node/node.go

@@ -713,7 +713,17 @@ func (n *Node) configureRPC() {
 	rpccore.SetConfig(*n.config.RPC)
 }
 
-func (n *Node) startRPC() ([]net.Listener, error) {
+func (n *Node) startRPC() (listeners []net.Listener, err error) {
+	defer func() {
+		if err != nil {
+			// Close all the created listeners on any error, instead of
+			// leaking them: https://github.com/gnolang/gno/issues/3639
+			for _, ln := range listeners {
+				ln.Close()
+			}
+		}
+	}()
+
 	listenAddrs := splitAndTrimEmpty(n.config.RPC.ListenAddress, ",", " ")
 
 	config := rpcserver.DefaultConfig()
@@ -729,8 +739,8 @@ func (n *Node) startRPC() ([]net.Listener, error) {
 
 	// we may expose the rpc over both a unix and tcp socket
 	var rebuildAddresses bool
-	listeners := make([]net.Listener, len(listenAddrs))
-	for i, listenAddr := range listenAddrs {
+	listeners = make([]net.Listener, 0, len(listenAddrs))
+	for _, listenAddr := range listenAddrs {
 		mux := http.NewServeMux()
 		rpcLogger := n.Logger.With("module", "rpc-server")
 		wmLogger := rpcLogger.With("protocol", "websocket")
@@ -782,7 +792,7 @@ func (n *Node) startRPC() ([]net.Listener, error) {
 			)
 		}
 
-		listeners[i] = listener
+		listeners = append(listeners, listener)
 	}
 	if rebuildAddresses {
 		n.config.RPC.ListenAddress = joinListenerAddresses(listeners)