Finding all permutations of a string in Golang

permute.go

package main
import (
        "fmt"
        "strings"
)

var result []string

func main() {
        permuteString("", "golang")
        fmt.Printf("%d permutations found.\n", len(result))
}

func permuteString(prefix string, rem string) {
        if len(rem) == 0 {
                result = append(result, prefix)
                return
        }
        for i := 0; i < len(rem); i++ {
                //swap ith char with rem[0]
                //and trigger the next recursion.
                s := swap(rem, 0, i)
                p := prefix + string(s[0])
                newRem := s[1:]
                permuteString(p, newRem)
        }
}

func swap(s string, i int, j int) string {
        ith := s[i]
        jth := s[j]
        var sb strings.Builder
        for m := 0; m < len(s); m++ {
                if m == i {
                        sb.WriteByte(jth)
                        continue
                }
                if m == j {
                        sb.WriteByte(ith)
                        continue
                }
                sb.WriteByte(s[m])
        }
        return sb.String()
}