Why optional request parameter is not a pointer type generated by goctl api

[Tony7817]

Describe the bug
one block of my api is defined as:

	StarListRequest {
		Keyword string `json:"keyword,optional"`
		Page    int64  `json:"page"`
		Size    int64  `json:"size"`
	}

The keyword is optional. When I generate my code with goctl. The types.go is shown as blow:

type StarListRequest struct {
	Keyword string `json:"keyword,optional"`
	Page    int64  `json:"page"`
	Size    int64  `json:"size"`
}

Why the Keyword is not a pointer since it's optional?
Let's see the protobuf's generation:

// .proto defination:
   message StarListRequest {
    int64 Page = 1;
    int64 Limit = 2;
    optional string Keyword = 3;

The code generated:

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

	Page    int64   `protobuf:"varint,1,opt,name=Page,proto3" json:"Page,omitempty"`
	Limit   int64   `protobuf:"varint,2,opt,name=Limit,proto3" json:"Limit,omitempty"`
	Keyword *string `protobuf:"bytes,3,opt,name=Keyword,proto3,oneof" json:"Keyword,omitempty"`
}

See? It's a pointer. If api's generation of this field is not a pointer, it will be a trouble in api logic. since you have to do a if judgement to conver the filed to a pointer before you call rpc server.

2. The error is

Expected behavior
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Screenshots
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Environments (please complete the following information):

• OS: [e.g. Linux]
• go-zero version [e.g. 1.2.1]
• goctl version [e.g. 1.2.1, optional]

More description
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[Tony7817]

You have to mark it as a pointer in .api file.

	StarListRequest {
		Keyword *string `json:"keyword,optional"`
		Page    int64   `json:"page"`
		Size    int64   `json:"size"`
	}