Change pipeline to use netcore 3.0 for build (#115)

Change pipeline to use netcore 3.0 for build

azure-pipelines.yml

@@ -12,21 +12,21 @@ pool:
 
 
 steps:
-- task: NuGetToolInstaller@0
-  displayName: 'Use NuGet 4.7.1'
+- task: UseDotNet@2
+  displayName: 'Use .NET Core sdk 2.2'
   inputs:
-    versionSpec: 4.7.1
-  enabled: true
+    version: 2.2.x
 
-- task: NuGetCommand@2
-  displayName: 'NuGet restore'
-  enabled: true
+- task: UseDotNet@2
+  displayName: 'Use .NET Core sdk 3.0'
+  inputs:
+    version: 3.0.x
 
 - task: DotNetCoreCLI@2
   displayName: 'dotnet build'
   inputs:
     projects: '**\*.sln'
-    arguments: '-c Release  -p:Platform=x64 --no-restore'
+    arguments: '-c Release  -p:Platform=x64'
 
 - task: DotNetCoreCLI@2
   displayName: 'dotnet test'