Example 08: External Proto — Different go_package

This example demonstrates importing proto files from an external directory where the files have different go_package values, requiring cross-package imports in the generated Go code.

Proto Definition

The proto files use different go_package values:

• service.proto: go_package = "example.com/demo/pb"
• ext_protos/common/types.proto: go_package = "example.com/demo/pb/common"

Source layout:

08-external-proto-diff-pkg/
├── ext_protos
│   └── common
│       └── types.proto    # External proto (go_package = "example.com/demo/pb/common")
├── service.proto          # Service definition (go_package = "example.com/demo/pb")
├── README.md
└── README-cn.md

• types.proto has go_package = "example.com/demo/pb/common" — a different Go package.
• service.proto uses common.ExtReq / common.ExtReply directly as RPC parameter types.

Generation Commands

First, initialize the output directory with a go.mod:

mkdir -p output && cd output && go mod init example.com/demo && cd ..

Then generate the code (note -I ./ext_protos):

goctl rpc protoc service.proto \
  --go_out=output \
  --go-grpc_out=output \
  --zrpc_out=output \
  --go_opt=module=example.com/demo \
  --go-grpc_opt=module=example.com/demo \
  --module=example.com/demo \
  -I . -I ./ext_protos

Generated directory structure:

output/
├── dataservice
│   └── dataservice.go
├── etc
│   └── svc.yaml
├── go.mod
├── internal
│   ├── config
│   │   └── config.go
│   ├── logic
│   │   └── fetchlogic.go
│   ├── server
│   │   └── dataserviceserver.go
│   └── svc
│       └── servicecontext.go
├── pb
│   ├── common
│   │   └── types.pb.go
│   ├── service.pb.go
│   └── service_grpc.pb.go
└── svc.go

Key Points

• When the external proto has a different go_package, goctl generates cross-package Go imports automatically.
• goctl resolves the proto package name (e.g., common) to the correct Go import path by parsing the imported proto's go_package option.
• service.proto uses common.ExtReq / common.ExtReply directly as RPC parameter types.