On running \'pack\' I am getting the following error...
2017-07-05T10:37:09.7762333Z ##[section]Starting: NuGet pack 2017-07-05T10:37:09.7762333Z ===========
In VSTS I used "dotnet pack" instead of "nuget pack". So this problem was resolved.
To publish nuget lib on VSTS, I choiced the following plugins sequence: