Why there is no Code about service in .pb.swift

[Lee-1991]

There are some code about service in my .proto, after "protoc --swift_out=. im.proto" ,there is no code about service that I wanted in .pb.swift
service IM {
// 客户端发送消息
rpc SendMsg (SendMessage) returns (SendResult) {}
// 服务端推送新消息
rpc NewMsg (EmptyRequest) returns (stream NewMessage) {}
}

[thomasvl]

This has come up before, check out #793, #682 and #118.