How do I pass a json body request to api in a map string data structure in Golang?

I am new to golang and grpc, need guidance and clarification. I have below definition as a parameter to call a POST request for an external API.

    params := map[string]string{
    "movie":       movie,
    "seat":         seat,
    "pax": fmt.Sprint(pax),
    "class":      class,
}

In proto file, I have below:

message TicketData {
    string movie= 1;
    string seat= 2;
    uint32 pax= 3;
    string class = 4;
}

message SearchMovieRequest {
    TicketData data= 1;
}

However in POSTMAN (grpc request), the body request is showing below:

{
    "data": 
        {
            "movie": "abc",
            "seat": "123",
            "pax": 2,
            "class ": "b""
        }
   
}

the request body should be below:

{
    "data": **[**
        {
            "movie": "abc",
            "seat": "123",
            "pax": 2,
            "class ": "b""
        }
    **]** - missing brackets in my json body
}

I have tried using structpb and also map string interface. It doesn't seem to work. Any pointer will be appreciated. Thank you.

You want the data field to be repeated TicketData.

See e.g. Specifying Field Rules in the Protobuf Language Guide (proto3).

Specifically:

message TicketData {
    string movie= 1;
    string seat= 2;
    uint32 pax= 3;
    string class = 4;
}

message SearchMovieRequest {
    repeated TicketData data= 1;
}

NOTE Although you include protobuf definitions, your examples are JSON. Protobuf implementations usually include automatic mappings between protobuf and JSON which is -- I assume -- what you're presenting.