In a clean project (generated with dotNET CLI) make a new folder in the Healthy.API folder with command mkdir Models
and add some models there.
Add packages
dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet restore
Open csproj file, Healthy.API.csproj and make sure <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.0.1" />
has been added as below.