Add Go hello world verification example

[sureshchouksey8]

Summary

• Add a minimal examples/hello-world/go example using only Go standard library packages.
• Call APort's /api/verify/policy/{policy} endpoint and print the allow decision plus any returned reasons.
• Document environment variables and run instructions.

Verification

• Reviewed for standard-library-only Go implementation.
• git diff --check
• Go toolchain is not installed in this Codex environment, so I could not run go run main.go locally.

/claim #27

[sureshchouksey8]

This is ready for review. It adds the requested Go hello-world verification example under examples/hello-world/go with a README and a minimal runnable program.