Declare support for async 2.0.0 (flutter#9)

Author: nex3

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.0.6
+
+* Declare support for `async` 2.0.0.
+
 ## 1.0.5
 
 * Increase the SDK version constraint to `<2.0.0-dev.infinity`.

pubspec.yaml

@@ -1,5 +1,5 @@
 name: web_socket_channel
-version: 1.0.6-dev
+version: 1.0.6
 description: StreamChannel wrappers for WebSockets.
 author: Dart Team <[email protected]>
 homepage: https://github.com/dart-lang/web_socket_channel
@@ -8,7 +8,7 @@ environment:
   sdk: '>=1.13.0 <2.0.0'
 
 dependencies:
-  async: '^1.3.0'
+  async: '>=1.3.0 <3.0.0'
   crypto: '>=0.9.2 <3.0.0'
   stream_channel: '^1.2.0'