gistfile1.cs

protected override void Initialize()
{ 
    //Other stuff...
    ...
    
    var componentModel = (IComponentModel)Microsoft.VisualStudio.Shell.Package.GetGlobalService(typeof(SComponentModel));
    var workspace = componentModel.GetService<Microsoft.VisualStudio.LanguageServices.VisualStudioWorkspace>();
}

//Alternatively you can MEF import the workspace. This has given me a lot of problems, 
//so I prefer not to use MEF here, but here's how you'd import it as a property.

[Import(typeof(Microsoft.VisualStudio.LanguageServices.VisualStudioWorkspace))]
public VisualStudioWorkspace myWorkspace { get; set; }