Find anagramms in go

anagramm.go

package main

import (
	"bufio"
	"log"
	"os"
	"strings"
)

func main() {
	var anagramm = make(map[string]int, 2^20)
	var sawBefore = make(map[string]bool, 2^20)

	file, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatal(err)
	}

	defer file.Close()

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		word := strings.ToLower(scanner.Text())

		if _, ok := sawBefore[word]; ok {
			continue
		}
		sawBefore[word] = true

		signature := makeSig(word)
		if _, ok := anagramm[signature]; !ok {
			anagramm[signature]++
		} else {
			anagramm[signature]++
		}
	}

}

func makeSig(s string) string {
	if len(s) == 1 {
		return s
	}

	/* reserve memory for runes */
	r := make([]rune, len(s))

	/* Copy string runes to arrays of rune */
	for k, v := range s {
		r[k] = v
	}

	/* Sort runes by selection sort */
	for i := 0; i < len(r); i++ {
		pos := i
		for j := i + 1; j < len(r); j++ {
			if r[j] < r[pos] {
				pos = j
			}
		}

		if pos != 0 {
			r[pos], r[i] = r[i], r[pos]
		}
	}

	/* return string */
	return string(r)
}