How to get namespace using microsoft.aspnetcore.hosting.internal;

There is no Microsoft.AspNetCore.Hosting.Internal namespace. It doesn't exist.

There is a Microsoft.AspNetCore.Hosting namespace:
Microsoft.AspNetCore.Hosting Namespace | Microsoft Learn[^]

To use that namespace from a project using the Microsoft.NET.Sdk SDK, you need to add a framework reference to your project:

<ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
</ItemGroup>

If your project uses the Microsoft.NET.Sdk.Web SDK, that reference is included automatically.

Use ASP.NET Core APIs in a class library | Microsoft Learn[^]