Swagger Example Response Have Field With Value Null

[Hidayathamir]

Additional context
I want my swagger example response have field with value null

question step

1. package model

package model

type SwaggerResponseNotFoundTest struct {
    Status       int         `json:"status" example:"404"`
    Data         interface{} `json:"data"`
    ErrorMessage interface{} `json:"error_message" swaggertype:"string" example:"No data found"`
}

2. use struct for documentation

package controller

// @Failure    404    {object}    model.SwaggerResponseNotFoundTest{}
func (ctrl *Controller) Foo(c *gin.Context) {
}

3. generate docs

$ swag init

will generate

        "model.SwaggerResponseNotFoundTest": {
            "type": "object",
            "properties": {
                "data": {},
                "error_message": {
                    "type": "string",
                    "example": "No data found"
                },
                "status": {
                    "type": "integer",
                    "example": 404
                }
            }
        },

question: what should i do so it will generate

        "model.SwaggerResponseNotFoundTest": {
            "type": "object",
            "properties": {
                "data": {
                    "nullable": true,
                    "example": null
                },
                "error_message": {
                    "type": "string",
                    "example": "No data found"
                },
                "status": {
                    "type": "integer",
                    "example": 404
                }
            }
        },

the different is in

                "data": {
                    "nullable": true,
                    "example": null
                },

---

Swag version

$ swag --version
swag version v1.8.12

Go version

$ go version
go version go1.20.6 linux/amd64

Desktop (please complete the following information):

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 22.04.2 LTS
Release:        22.04
Codename:       jammy