Go: Realtime Transcription example with AWS Transcribe using microphone as input source

[sumit-anantwar]

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[Laren-AWS]

Thanks for your contribution!

However, I encountered some issues:

• My attempts to install and compile portaudio for Windows did not work. It looks like the project versions are too old to convert properly, and I'm concerned customers would encounter this issue as well when trying to run this example. I recommend either finding a newer library for audio or simplifying the example to work from prerecorded audio files instead of including the microphone as part of the example.
• Your example doesn't follow all of our current standards such as loading default AWS credentials, handling errors, and including unit and/or integration tests.

I'm closing this PR for now, but feel free to make the above changes and reopen, thanks!