Added go support and hello world example

[anfelbar]

About

Adding Go support and hello world example.
Run with bazel run //go

Progress #36

[TheGrizzlyDev]

Can we make the example less trivial? Maybe add some dependencies and more than just a file?

[anfelbar]

The first commits try to add support for the language. Maybe a test. This addresses this #36. I have no experience with go, scala, swift, so I am just adding a hello world example and continue from there as wee need to do some more work this repository #40.
Now, if you have a go example I can just copy and paste, then I change this PR, no problem whatsoever. Any example suggestion?

[jayconrod]

LGTM. Fine to start with a simple example, and we can expand it later. As an idea, I like small gRPC servers as Bazel examples, since it demonstrates code generation and cross-language projects. Also protoc is not a small tool, and if we can compile it very quickly on remote execution, that's a nice demo.

[jayconrod]

Probably out of scope for this PR but FYI: I think this will only work for remote execution if the execution platform is the same as the host platform. Our CI in this repo doesn't appear to cover remote execution.

[anfelbar]

Probably out of scope for this PR but FYI: I think this will only work for remote execution if the execution platform is the same as the host platform. Our CI in this repo doesn't appear to cover remote execution.

I think that's okay. These examples will be useful for running against a cluster with remote execution capabilities. I just ran it in our canary and it works. It is slow though.