vue js 2 tambah index array

bisa pakai second argument index (tanpa $)

<p v-for="(forum, index) in forums" data-index="{{index}}">{{forum}}</p>

maaf um ane udah coba tapi malah muncul error seperti ini

 [Vue warn]: Error compiling template:

<div id="app">
			<li v-for="(member, index) in  members" data-index="{{index}}">
				{{member.nama}} - {{member.umur}}
			</li>
			<!-- <div v-if="this.umur > 10">  -->
				<!-- {{ biodata }}  -->
			<!-- <div>  -->
		</div>

data-index="{{index}}": Interpolation inside attributes has been removed. Use v-bind or the colon shorthand instead. For example, instead of <div id="{{ val }}">, use <div :id="val">.

(found in <Root>)

tetapi jika saya coba mengeluarkan index seperti ini tidak ada

 <p v-for="(forum, index) in forums" data-index="">{{forum}} - {{index}}</p>