Set custom attribute on component and Retrieve that in controller

custom_attribite.cmp

<div class="slds-truncate" style ="text-align : center;" title="{!$Label.c.Selection}"  data-selected-Index = "{!com.key}" onclick ="{!c.setKey}">
    <lightning:input aura:id="selectedRange" name="radioButton" type="radio"/>
</div>

custom_attribiteController.js

setKey: function(component, event,helper) {
    var target = event.currentTarget;
    var dataEle = event.currentTarget.getAttribute("data-selected-Index");
    console.log("v.selectedItem", "Component at index "+dataEle+" has value "+target.value);
    component.set("v.commsListKey", dataEle);
}