Go lang create map from database results without using predefined struct

I created some function which get "random" data from MySQL database and return it as JSON. Here is some example code for achieve this, I skipped boring part with imports and creating net/http server and error handling is skipped.

db, _ := sql.Open("mysql", "user=demo dbname=demo password=test")
rows, _ := db.Query("select * from sites")
columns, _ := rows.Columns()
count := len(columns)
values := make([]interface{}, count)
valuePtrs := make([]interface{}, count)

final_result := map[int]map[string]string{}
result_id := 0

for rows.Next() {
	for i, _ := range columns {
		valuePtrs[i] = &values[i]
	}
	rows.Scan(valuePtrs...)

	tmp_struct := map[string]string{}

	for i, col := range columns {
		var v interface{}
		val := values[i]
		b, ok := val.([]byte)

		if (ok) {
			v = string(b)
		} else {
			v = val
		}

		tmp_struct[col] = fmt.Sprintf("%s", v)
	}

	final_result[result_id] = tmp_struct
	result_id++
}

fmt.Println(final_result)