They like to make noise about how crossplatform and opensource .NET Core is, but their debugging infrastructure is actually proprietary. See: https://github.com/dotnet/core/issues/505
actually this is not 100% correct.
it's actually possible to make your own debugger for dotnet core since the interfaces to create one are public and opensource. it's just that the debugger that microsoft has written, is not open source.
the "infrastructure for debugging" is actually open source.
have you read the github issue linked? make sure to read the comment from Alex