See http://www.blue.sky.or.jp/grass/doc_ja.html

kusa.go

package main

import (
    "fmt"
    "time"
    "math/rand"
)

func main() {
    n := 1000

    kusaChars := []rune{ 'w', 'W', 'v' }

    for i := 0; i < n; i ++ {
        fmt.Printf("%c", choice(kusaChars))
    }
    fmt.Println()
}

func choice(s []rune) rune {
    rand.Seed(time.Now().UnixNano())
    i := rand.Intn(len(s))
    return s[i]
}