ISSUE-333: End to End Message Encryption Support in GO Client

[sijie]

Original Issue: apache#333

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Is your feature request related to a problem? Please describe.
Currently End to End Encryption is not support for the Pulsar GO Client Library. As a user of Pulsar I have many services that are in GO and Java. I would like to leverage message encryption for all my services. Currently it can be done with my clients written in Java, but not in GO.

Describe the solution you'd like
I've taken a look at the research here https://github.com/apache/pulsar/wiki/PIP-4:-Pulsar-End-to-End-Encryption
Also at the changes made for the java client library https://github.com/apache/pulsar/pull/731/files

Basically it would be the same solution implemented in GO. I know there is support in the C++ and Java libraries.

Describe alternatives you've considered
I was potentially looking at using the c++ solution with GO. I'm not sure if it would be possible. I saw support for encryption for c++ here https://github.com/apache/pulsar/blob/master/pulsar-client-cpp/include/pulsar/ConsumerConfiguration.h#L228

Also I know there is a CGO Library. https://pulsar.apache.org/docs/en/client-libraries-cgo/

I'm not sure if they would be compatible though.