Add integration module for dubbo-go

[louyuting]

Issue Description

Type: feature request

Describe what feature you want

Add integration module for dubbo-go client and server.

Additional context

Discussions are welcomed!

Add any other context or screenshots about the feature request here.

[pantianying]

dubbo-go provides a filter mechanism, which makes it easy to set a custom filter. We just need to implement the following filter interface：

And before the config. Load() function, call the Setfilter() function to partition the filter instance into the filter library.
then use like the following configfile to use sentinel

[sczyh30]

Resolved via #60.