go get -u github.com/NYTimes/openapi2proto/cmd/openapi2proto

╰─➤  openapi2proto -spec swagger.yaml -annotate
syntax = "proto3";

package swaggerpetstore;

import "google/api/annotations.proto";
import "google/protobuf/empty.proto";

message AddPetRequest {
    message PetMessage {
        int64 id = 1;
        string name = 2;
        string tag = 3;
    }

    // Pet to add to the store
    PetMessage pet = 1;
}

message AddPetResponse {
    int64 id = 1;
    string name = 2;
    string tag = 3;
}

message DeletePetRequest {
    // ID of pet to delete
    int64 id = 1;
}

message FindPetByIdRequest {
    // ID of pet to fetch
    int64 id = 1;
}

message FindPetByIdResponse {
    int64 id = 1;
    string name = 2;
    string tag = 3;
}

message FindPetsByIdsRequest {
    repeated string ids = 1;

    // maximum number of results to return
    int32 limit = 2;
}

message FindPetsByIdsResponse {
    message PetsMessage {
        int64 id = 1;
        string name = 2;
        string tag = 3;
    }

    repeated PetsMessage pets = 1;
}

message FindPetsRequest {
    // maximum number of results to return
    int32 limit = 1;

    // tags to filter by
    repeated string tags = 2;
}

message FindPetsResponse {
    message PetsMessage {
        int64 id = 1;
        string name = 2;
        string tag = 3;
    }

    repeated PetsMessage pets = 1;
}

service SwaggerPetstoreService {
    // Creates a new pet in the store.  Duplicates are allowed
    rpc AddPet(AddPetRequest) returns (AddPetResponse) {
        option (google.api.http) = {
            post: "/api/pets"
            body: "pet"
        };
    }

    // deletes a single pet based on the ID supplied
    rpc DeletePet(DeletePetRequest) returns (google.protobuf.Empty) {
        option (google.api.http) = {
            delete: "/api/pets/{id}"
        };
    }

    // Returns a user based on a single ID, if the user does not have access to the pet
    rpc FindPetById(FindPetByIdRequest) returns (FindPetByIdResponse) {
        option (google.api.http) = {
            get: "/api/pets/{id}"
        };
    }

    // Returns all pets from the system that the user has access to
    rpc FindPets(FindPetsRequest) returns (FindPetsResponse) {
        option (google.api.http) = {
            get: "/api/pets"
        };
    }

    // Returns all pets from the system that the user has access to
    rpc FindPetsByIds(FindPetsByIdsRequest) returns (FindPetsByIdsResponse) {
        option (google.api.http) = {
            get: "/api/pets/{ids}"
        };
    }
}