Add packageSourceMapping to match the custom nuget packageSource

nuget.config

@@ -10,4 +10,9 @@
     <clear />
     <add key="nuget" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
   </packageSources>
-</configuration>
+  <packageSourceMapping>
+    <packageSource key="nuget">
+      <package pattern="*" />
+    </packageSource>
+  </packageSourceMapping>
+</configuration>