gRPC generated file doesn't have json definition

I’m trying to generate Go file from proto file but it doesn’t have json definition in the method’s input definition. Should I add the json definition by myself or there were something wrong with my script. Thank you, I sincerely appreciate your help.

Proto file

message RateRequest {
    string Base = 1;
    string Destination = 2;
}

Generated file

type RateRequest struct {
    state         protoimpl.MessageState
    sizeCache     protoimpl.SizeCache
    unknownFields protoimpl.UnknownFields

    //No json definition here
    Base        string `protobuf:"bytes,1,opt,name=Base,proto3" json:"Base,omitempty"`
    Destination string `protobuf:"bytes,2,opt,name=Destination,proto3" json:"Destination,omitempty"`
}

Protoc script

protoc --go_out=. --go_opt=paths=source_relative \
--go-grpc_out=. --go-grpc_opt=paths=source_relative \
protos/currency.proto

grpcurl

grpcurl --plaintext -d '{Base: "GBP", Destination: "USD"}' localhost:9092 Currency.GetRate
// Error invoking method "Currency.GetRate": error getting request data: message type RateRequest has no known field named base

>Solution :

Since the error is

error getting request data: message type RateRequest has no known field named base

And the json is

json:"Base,omitempty"`

Then it seems it’s looking for the wrong field, it should be

json:"base,omitempty"`