Update dotnet.yml

Author: artemutin

.github/workflows/dotnet.yml

@@ -46,7 +46,7 @@ jobs:
         # Format of the git tag, [*] gets replaced with actual version
         #TAG_FORMAT: # optional, default is v*
         # API key to authenticate with NuGet server
-        #NUGET_KEY: # optional
+        NUGET_KEY: $NUGET_KEY
         # NuGet server uri hosting the packages, defaults to https://api.nuget.org
         #NUGET_SOURCE: # optional, default is https://api.nuget.org
         # Flag to toggle pushing symbols along with nuget package to the server, disabled by default