How to return interface list from a for loop in Go?

How to return interface list from a for loop in Go?
Supposed I have data as below:

I can use the below go code to get two list of project_type=1 and project_type=2,

func (d *db) ProjectList(Type, uid string, size uint64) (interface{}, interface{}, error) {
    type resp struct {
        Name            string  `json:"name"`
        Id             string  `json:"id"`
        ProjectType    string  `json:"project_type"`

    }

    var project_type_1 []*resp
    var project_type_2 []*resp

    sql = fmt.Sprintf(sql, where.String())
    _, err := d.ctx.DB().SelectBySql("select * from project where project_type=1 order by rand() limit 10").Load(&project_type_1)

    _, err = d.ctx.DB().SelectBySql("select * from project where project_type=2 order by rand() limit 10").Load(&project_type_2)
    return project_type_1, project_type_2, err
}

But now the data of project_type is a JSON of [{"project_type":1,"name":"something else"},{"project_type":2,"name":"something else"},{"project_type":3,"name":"something else"},{"project_type":4,"name":"something else"}], project_type is more than 2, I have to get a interface{} list, I tried to re-write code as below, But I don't know how do write next, How to return interface list from a for loop in Go?, thanks so much for any advice.

func NewProjectList(d *db) ([]interface{}, error) {
    var s = make([]ProjectType, 0)
    data, err := d.QueryString("project_type")
    if err != nil {
        return nil, err
    }

    err = json.Unmarshal([]byte(data), &s)
    if err != nil {
        return nil, err
    }

    for _, shortType := range s {
        fmt.Println("this is shortType", shortType)
    }
    return nil, err

}

if you want each project_type have 10 results(all 10*n results):

func (d *db) ProjectList(Type, uid string, size uint64) ([]interface{}, error) {
	type resp struct {
		Name        string `json:"name"`
		Id          string `json:"id"`
		ProjectType string `json:"project_type"`
	}
	// get all types, you can get it from db
	// example: select DISTINCT ProjectType from project
	types := []string{"1", "2", "3", "4"}
	ans := []interface{}{}

	for _, sType := range types {
		var project_type []*resp
		sql = fmt.Sprintf(sql, where.String())
		_, err := d.ctx.DB().SelectBySql("select * from project where project_type=" + sType + " order by rand() limit 10").Load(&project_type)
		ans = append(ans, project_type)
	}
	return ans, nil
}

if A total of 10 results for all types:

 i write it if you need it