1.The Go code generator does not produce output for services by default.
 	If you enable the gRPC plugin (see the gRPC Go Quickstart guide) then code will be generated to support gRPC.
2.*.pb.go
	Code for populating, serializing, and retrieving * message types
3.*_grpc.pb.go
	Generated client and server code
4.how to generate *.pb.go and *_grpc.pb.go
	protoc -I$GOPATH/src -I. --go-grpc_out=$GOPATH/src example.proto
	protoc -I$GOPATH/src -I. --go_out=$GOPATH/src example.proto