Updated doc

README.md

@@ -20,7 +20,7 @@ steps:
 - uses: actions/checkout@master
 - uses: actions/setup-dotnet@v1
   with:
-    dotnet-version: '3.1.100' # SDK Version to use.
+    dotnet-version: '3.1.x' # SDK Version to use. x will use the latest version of the 3.1 channel
 - run: dotnet build <my project>
 ```
 

action.yml

@@ -6,7 +6,7 @@ branding:
   color: green
 inputs: 
   dotnet-version:
-    description: 'SDK version to use. Example: 2.2.104'
+    description: 'SDK version to use. Examples: 2.2.104, 3.1, 3.1.x'
   source-url:
     description: 'Optional package source for which to set up authentication. Will consult any existing NuGet.config in the root of the repo and provide a temporary NuGet.config using the NUGET_AUTH_TOKEN environment variable as a ClearTextPassword'
   owner: