Add GitHub Actions CI workflow to verify compatibility across multiple Go versions

[Copilot]

This PR adds continuous integration support to automatically verify the compatibility of the codebase across different Go versions.

Changes

Added .github/workflows/go.yml with a GitHub Actions workflow that:

• Tests across 13 Go versions: From Go 1.13 (the minimum version specified in go.mod) through Go 1.25
• Runs on every push to the master branch to catch compatibility issues early
• Validates pull requests before merging to ensure new changes work across all supported versions
• Performs comprehensive checks including:
  • Dependency resolution (go mod download)
  • Build verification (go build -v ./...)
  • Test execution (go test -v ./...)

Why this matters

The repository currently requires Go >= 1.9 (as documented in cmd/pkgimport/README.md) and specifies Go 1.13 in go.mod. Without automated testing, it's difficult to ensure the codebase remains compatible with both older and newer Go versions as changes are made. This CI workflow provides immediate feedback on compatibility issues, helping maintain the project's commitment to supporting a wide range of Go versions.

Testing

The workflow uses GitHub Actions' matrix strategy to run tests in parallel across all specified Go versions, providing efficient and comprehensive coverage. Each version is tested independently to catch version-specific issues.

Fixes #5

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add CI to verify the compatibility of different Go versions</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #5

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