Added CORS support for golang image for PR #934

[vallard]

Issue Ref: #934

Description:
Add CORS to golang runtime.

[PR Description]
Added headers for CORS to the golang runtime.

TODOs:

• Ready to review
• Automated Tests
• Docs

[andresmgot]

thanks for the PR! I have a suggestion

[andresmgot]

I would suggest to accept any request and let the user function deal with methods/headers. For doing so, and for consistency with the NodeJS approach, we can just return the same headers received. Also, I think we should just set these headers when the request is a CORS request:

w.Header().Set("Access-Control-Allow-Origin", "*")
if r.Method == "OPTIONS" {
  w.Header().Set("Access-Control-Allow-Methods", r.Header.Get("access-control-request-method"))
  w.Header().Set("Access-Control-Allow-Headers", r.Header.Get("access-control-request-headers"))
  return
}

[andresmgot]

Hi @vallard, we have migrated the code of the runtimes to this new repository: https://github.com/kubeless/runtimes

I have migrated your proposal to this PR: vmware-archive/runtimes#9 please take a look if you have a chance. I am closing the PR in this repo.