Fix plugin-go-grpc example (#66)
Fix plugin-go-grpc example (#66)

This commit fixes the plugin-go-grpc example to use the updated
GRPCPlugin interface introduced in #52 and #55.

Prior to this change attempts to initialise the plugin would fail
with an `is not a GRPC-compatible plugin` error.

Signed-off-by: John McCabe <a51dda7c7ff50b61eaea0444371f4a6a9301e501@johnmccabe.net>
hashicorp/go-plugin