codewars/go/stepik/3/interface_task2.go

package main

import (
	"fmt"
	"strings"
)

type battery uint8

func (b *battery) set(str string) {
	*b = battery(strings.Count(str, `1`))
}

func (b battery) String() string {
	return fmt.Sprintf("[%10s]", strings.Repeat("X", int(b)))
}

func main() {
	var batteryForTest battery
	var str string
	fmt.Scan(&str)
	batteryForTest.set(str)
	fmt.Println(batteryForTest)
}