Streaming

protogen generates all four gRPC RPC kinds, using grpc-go's generics-based stream types (the shape protoc-gen-go-grpc v1.6+ emits).

service Chat {
  rpc Send(Message) returns (Ack);                        // unary
  rpc Subscribe(SubscribeRequest) returns (stream Message);   // server streaming
  rpc Upload(stream Chunk) returns (UploadSummary);       // client streaming
  rpc Converse(stream Message) returns (stream Message);  // bidirectional
}

Generated gRPC

The client interface and server interface adapt to each kind:

type ChatClient interface {
	Send(ctx context.Context, in *Message, opts ...grpc.CallOption) (*Ack, error)
	Subscribe(ctx context.Context, in *SubscribeRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[Message], error)
	Upload(ctx context.Context, opts ...grpc.CallOption) (grpc.ClientStreamingClient[Chunk, UploadSummary], error)
	Converse(ctx context.Context, opts ...grpc.CallOption) (grpc.BidiStreamingClient[Message, Message], error)
}

type ChatServer interface {
	Send(context.Context, *Message) (*Ack, error)
	Subscribe(*SubscribeRequest, grpc.ServerStreamingServer[Message]) error
	Upload(grpc.ClientStreamingServer[Chunk, UploadSummary]) error
	Converse(grpc.BidiStreamingServer[Message, Message]) error
	mustEmbedUnimplementedChatServer()
}

The ServiceDesc places unary methods in Methods and streaming methods in Streams with the correct ServerStreams/ClientStreams flags — so the code works against the standard grpc-go runtime unchanged.

Streaming over the gateway

Only server-streaming methods can be exposed over REST. When a server-streaming method has a google.api.http binding, the gateway forwards each message as a chunked JSON stream (runtime.ForwardResponseStream):

rpc Subscribe(SubscribeRequest) returns (stream Message) {
  option (google.api.http) = { get: "/v1/rooms/{room}/messages" };
}

GET /v1/rooms/general/messages
{"result":{"room":"general","text":"msg 0"}}
{"result":{"room":"general","text":"msg 1"}}
...

Notes:

• The in-process Register<Service>HandlerServer path returns Unimplemented for streaming methods (matching protoc-gen-grpc-gateway); use Register<Service>Handler over a real connection for streaming.
• Client-streaming and bidirectional methods have no REST representation, so the gateway skips them (it prints a note to stderr). They remain fully available over gRPC.
• additional_bindings are out of scope.