I don't know what type of field type to specify in the message type in the proto file.

We create proto files, create microservices with Go and Nxt, and develop services that communicate with gRPC.

In order to realize a certain functionality, I am thinking of sending the acquired data to the front service as a response using the YouTube Data API.

The response of the Youtube Data API is returned as a JSON object, but I do not know how to specify the field type in the proto file message type, so I am thinking about it for a long time.

message ChannelListResponse{
   channel_list=1;
}

I would appreciate your advice.