fix(agent): retire replaced tunnel sessions (#541)

go-gost/x/dialer/kcp/dialer_test.go

@@ -0,0 +1,17 @@
+package kcp
+
+import (
+	"context"
+	"errors"
+	"net"
+	"testing"
+)
+
+func TestRetiredDialerRejectsNewConnections(t *testing.T) {
+	dialer := NewDialer().(*kcpDialer)
+	dialer.Retire()
+
+	if _, err := dialer.Dial(context.Background(), "127.0.0.1:1"); !errors.Is(err, net.ErrClosed) {
+		t.Fatalf("Dial error = %v, want net.ErrClosed", err)
+	}
+}