modify reqeust form in request body in fiber framework

I'm working with the Fiber framework in Go and need to modify the request body to include URL parameters. Specifically, I want to combine both the request body and URL parameters into a single request form.

I've searched the Fiber documentation, but I couldn't find a function similar to setBody in the context (c). Also, I'd prefer not to use c.Local() for this purpose.

Has anyone encountered this situation or have a solution?

func AddParamToBody(paramName string) fiber.Handler {
    return func(c *fiber.Ctx) error {
        paramValue := c.Params(paramName)
        var bodyMap map[string]interface{}
        json.Unmarshal(c.Body(), &bodyMap); 
        bodyMap[paramName] = paramValue
        newBody, err := json.Marshal(bodyMap)
        
        // this is caused error, no SetBody() function exist in fiber framework
        c.SetBody(newBody)        // error

        return c.Next()
    }
}

I find the solution, you can't directly use SetBody() function, you sould call Request() function first.

c.Request().SetBody()