Draft a new version 0.4.0 (#67)

diff --git a/release.md b/release.md
index ff34dc1..42b6679 100644
--- a/release.md
+++ b/release.md
@@ -1,7 +1,10 @@
 # Release Guide
 All committer should follow these steps to do release for this repo.
 
-1. Update the [CHANGES.md](CHANGES.md) to prepare the official release.
+1. Prepare the official release.
+
+- Update the [CHANGES.md](CHANGES.md).
+- Create a new `skywalking-nginx-lua-x.y-z.rockspec` file under [rockspec](/rockspec).
 
 2. Package the source release.
 
diff --git a/rockspec/skywalking-nginx-lua-0.4-0.rockspec b/rockspec/skywalking-nginx-lua-0.4-0.rockspec
new file mode 100644
index 0000000..10ba4d6
--- /dev/null
+++ b/rockspec/skywalking-nginx-lua-0.4-0.rockspec
@@ -0,0 +1,33 @@
+package = "skywalking-nginx-lua"
+version = "0.4-0"
+source = {
+   url = "git://github.com/apache/skywalking-nginx-lua",
+   branch = "v0.4.0",
+}
+
+description = {
+   summary = "The Nginx Lua agent for Apache SkyWalking",
+   homepage = "https://github.com/apache/skywalking-nginx-lua",
+   license = "Apache License 2.0"
+}
+
+dependencies = {
+   "lua-resty-http >= 0.15",
+   "lua-resty-jit-uuid >= 0.0.7"
+}
+
+build = {
+   type = "builtin",
+   modules = {
+      ["skywalking.client"] = "lib/skywalking/client.lua",
+      ["skywalking.correlation_context"] = "lib/skywalking/correlation_context.lua",
+      ["skywalking.management"] = "lib/skywalking/management.lua",
+      ["skywalking.segment_ref"] = "lib/skywalking/segment_ref.lua",
+      ["skywalking.segment"] = "lib/skywalking/segment.lua",
+      ["skywalking.span_layer"] = "lib/skywalking/span_layer.lua",
+      ["skywalking.span"] = "lib/skywalking/span.lua",
+      ["skywalking.tracer"] = "lib/skywalking/tracer.lua",
+      ["skywalking.tracing_context"] = "lib/skywalking/tracing_context.lua",
+      ["skywalking.util"] = "lib/skywalking/util.lua",
+   }
+}