Declare support for async 2.0.0 (#5)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a3cb13f..824ba46 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.0.4
+
+* Declare support for `async` 2.0.0.
+
 ## 2.0.3
 
 * Fix `HttpMultiServer.loopback()` and `.loopbackSecure()` for environments that
diff --git a/pubspec.yaml b/pubspec.yaml
index 243e070..7d4114a 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: http_multi_server
-version: 2.0.4-dev
+version: 2.0.4
 author: "Dart Team <misc@dartlang.org>"
 homepage: https://github.com/dart-lang/http_multi_server
 description:
@@ -7,7 +7,7 @@
 environment:
   sdk: ">=1.13.0 <2.0.0"
 dependencies:
-  async: "^1.2.0"
+  async: ">=1.2.0 <3.0.0"
 dev_dependencies:
   test: ">=0.12.0 <0.13.0"
   http: ">=0.11.0 <0.12.0"