I\'ve been looking for any way to set the CopyToOutput attribute to true for content files I\'m including in a nuget package built in VS2017 from a .Net Standard Library pro
see https://github.com/NuGet/NuGet.Client/pull/1450 Allow specifying copyToOutput and flatten as Metadata on Content items when packing sdk csproj
You'll need to set PackageCopyToOutput to true in the source csproj for the content.
<Content Include="...">
<PackageCopyToOutput>true</PackageCopyToOutput>
</Content>
and once build the package, it will include CopyToOutput="true" for that content.