Task
Produce an ASCII representation of a Sierpinski triangle of order   N.



Example
The Sierpinski triangle of order   4   should look like this:

                       *
                      * *
                     *   *
                    * * * *
                   *       *
                  * *     * *
                 *   *   *   *
                * * * * * * * *
               *               *
              * *             * *
             *   *           *   *
            * * * *         * * * *
           *       *       *       *
          * *     * *     * *     * *
         *   *   *   *   *   *   *   *
        * * * * * * * * * * * * * * * *



Related tasks
 Sierpinski triangle/Graphical for graphics images of this pattern. 
 Sierpinski carpet


package main
 
import (
    "fmt"
    "strings"
    "unicode/utf8"
)
 
var order = 4
var grain = "*"
 
func main() {
    t := []string{grain + strings.Repeat(" ", utf8.RuneCountInString(grain))}
    for ; order > 0; order-- {
        sp := strings.Repeat(" ", utf8.RuneCountInString(t[0])/2)
        top := make([]string, len(t))
        for i, s := range t {
            top[i] = sp + s + sp
            t[i] += s
        }
        t = append(top, t...)
    }
    for _, r := range t {
        fmt.Println(r)
    }
}