func main() {
    text, err := getPluralItemText(1)
    if err != nil {
        log.Println(err)
    }
    fmt.Println(text)

    text, err = getPluralItemText(10)
    if err != nil {
        log.Println(err)
    }
    fmt.Println(text)
}

func getPluralItemText(count int) (string, error) {
    msg := plural.Selectf(1, "%d", plural.One, "%[1]d item", plural.Other, "%[1]d items")
    key := "%d item"
    tag := "en"

    lTag := language.MustParse(tag)

    err := message.Set(lTag, key, msg)
    if err != nil {
        return "", err
    }

    p := message.NewPrinter(language.English)
    s := p.Sprintf("%d item", count)
    return s, nil
}

Result

1 item
10 items