How to get the source of button in Lightning webcomponent

buttonFunctionality.html
========================
<template>
    <lightning-button-group>
<lightning-button label="Refresh" onclick={handleClick}>
</lightning-button>
<lightning-button label="Edit" onclick={handleClick}>
</lightning-button>
<lightning-button label="Save" onclick={handleClick}>
</lightning-button>
</lightning-button-group>
</template>

buttonFunctionality.js
======================
import { LightningElement,track } from 'lwc';

export default class buttonFunctionality extends LightningElement
{
    handleClick(event)
    {
        const buttonalabel=event.target.label;
        alert(buttonalabel);
    }
}

LighntingApplication
====================
<aura:application extends="force:slds">
    <c:buttonFunctionality/>
</aura:application>