add simple golang http endpoint example

[sebito91]

What did you implement:

Added a golang example of deploying a simple HTTP handler to AWS via hosted event-gateway.

How did you implement it:

Code mimics the example in the main serverless repo but instead of using AWS API Gateway we used the hosted EG.

How can we verify it:

sls deploy -v

Todos:

• Write tests
• Write documentation
• Fix linting errors
• Make sure code coverage hasn't dropped
• Provide verification commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[codecov]

Codecov Report

Merging #494 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #494   +/-   ##
======================================
  Coverage    71.2%   71.2%           
======================================
  Files          37      37           
  Lines        2195    2195           
======================================
  Hits         1563    1563           
  Misses        571     571           
  Partials       61      61

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