Container Files Support for Golang Integration ✅

This PR adds support for pushing files into Go containers, as requested in the issue.

Implementation Summary

• Added IContainerFilesDestinationResource interface implementation to GolangAppExecutableResource
• Set default container files destination to /app/static
• Added .AddContainerFiles() call in Dockerfile generation to handle container files
• Created comprehensive test coverage including integration test for publishing
• Updated documentation with usage examples
• Enhanced example application to demonstrate the feature
• All existing tests still passing (13/13 resource creation tests ✅)

Changes Made

1. Resource Implementation (GolangAppExecutableResource.cs)

public class GolangAppExecutableResource(string name, string workingDirectory)
    : ExecutableResource(name, "go", workingDirectory), 
      IResourceWithServiceDiscovery, 
      IContainerFilesDestinationResource
{
    public string ContainerFilesDestination => "/app/static";
}

2. Dockerfile Generation (GolangAppHostingExtension.cs)

• Added using Aspire.Hosting.ApplicationModel.Docker; to access AddContainerFiles extension method
• Added logger initialization from service provider
• Added .AddContainerFiles(context.Resource, "/app", logger) call in the Docker build chain to process container files

3. Documentation (README.md)

• Added detailed "Container Files Support" section
• Included usage examples for both static files and frontend resources
• Explained how the feature integrates with the publishing pipeline

4. Example Application

• Created static-frontend directory with sample HTML
• Added static file serving to Golang app (r.Static("/static", "./static"))
• Documented usage in Program.cs with commented examples

5. Testing

• Added test verifying interface implementation
• Added integration test for container files publishing support
• Validated default destination path
• All existing tests continue to pass (13 total tests passing)

Usage

Users can now copy files into Golang containers during publishing:

// From a static directory
var golang = builder.AddGolangApp("golang", "../gin-api")
    .WithHttpEndpoint(env: "PORT")
    .WithContainerFiles("/app/static", "../static-frontend");

// From a frontend build resource
var frontend = builder.AddViteApp("frontend", "../frontend");
var golang = builder.AddGolangApp("golang", "../gin-api")
    .WithContainerFiles("/app/static", frontend.Resource);

How It Works

1. GolangAppExecutableResource implements IContainerFilesDestinationResource (marker interface)
2. Users call WithContainerFiles to register files to copy
3. During publishing, the Dockerfile builder calls .AddContainerFiles() which:
   • Detects the interface implementation
   • Retrieves registered container files
   • Adds appropriate COPY instructions to the generated Dockerfile
4. The generated Docker image includes the copied files at the specified destination

Testing

✅ All 13 resource creation tests pass (including new integration test)
✅ Tests validate IContainerFilesDestinationResource implementation
✅ Tests verify container files support for publishing workflow
✅ Builds successfully across all target frameworks (net8.0, net9.0, net10.0)

Custom agent used: Hosting Integration Creator
This agent helps users create new hosting integration in Aspire by scaffolding the correct projects and files based on user input.

• Fixes Add support for pushing files into go containers #977

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