A perverted kind of natural sort in golang

natural_sort.go

package main

import (
        "fmt"
        "log"
        "sort"
        "strconv"
        "strings"
        "unicode"
)

// Mostly based on http://golang.org/pkg/sort/#example__sortKeys
// Since name is a string, don't need to implement fancy structs

type By func(name1, name2 string) bool

func (by By) Sort(names []string) {
        ps := &nameSorter{
                names: names,
                by:    by,
        }
        sort.Sort(ps)
}

type nameSorter struct {
        names []string
        by    func(name1, name2 string) bool
}

func getNumber(name string) (new_s int) {
        // Need a key to sort the names by. In this case, it's the number contained in the name
        // Example: M23abcdeg ---> 23
        // Of course, this tends to break hideously once complicated stuff is involved:
        // For example, 'ülda123dmwak142.e2dööööwq,' what do you sort by here?
        // Could be 123, could be 142, or 2, could be 1231422 (this takes the last case)

        s := make([]string, 0)
        for _, element := range name {
                if unicode.IsNumber(element) {
                        s = append(s, string(element))
                }
        }
        new_s, err := strconv.Atoi(strings.Join(s, ""))
        if err != nil {
                log.Fatal(err) // Just die
        }
        return new_s
}

// Need some inbuilt methods
func (s *nameSorter) Swap(i, j int) {
        s.names[i], s.names[j] = s.names[j], s.names[i]
}
func (s *nameSorter) Len() int {
        return len(s.names)
}
func (s *nameSorter) Less(i, j int) bool {
        return s.by(s.names[i], s.names[j])
}

func main() {
        // closure to sort by
        name_number := func(name1, name2 string) bool {
                return getNumber(name1) < getNumber(name2)
        }
        fmt.Println("Before:")
        example_slice := []string{"9999", "123bla", "1bla", "dawjdwa50awdnwdkj"}
        fmt.Println(example_slice)
        By(name_number).Sort(example_slice)
        fmt.Println("After:")
        fmt.Println(example_slice)
}