rocketmq-client-go-1.2.0

This release is the first initial golang client of rocketmq. It is based on the kernel of the CPP client and uses cgo to encapsulate the API Implementation of C.
The current version provides the following functions:

1. support reliable synchronous sending of messages;
2. support reliable orderly sending of messages;
3. support reliable push consuming model;
4. support default cluster consuming;
5. support delayed messages;
6. support reliable pull consuming model;
7. support custom message properties;
8. support message compression.
9. support oneway sending of messages;