vue elementui v-for loop el-table-column the first column of data changes to the last

When this dynamically renders the table table, it is found that the data in the first column of el-table-column has changed to the last one

The serial number is sorted to the back after
the code is modified

<el-table
      :data="tableData"
      tooltip-effect="dark"
      style="width: 100%"
      height="500"
    >
      
        <template v-for="(item, index) in columnList" >
            <el-table-column v-if="!item.children" :prop="item.prop" :label="item.label" :key="index">
            </el-table-column>
            <el-table-column v-else :prop="item.prop" :label="item.label" :key="index">
              <div v-for="(items, indexs) in item.children" :key="indexs">
                <el-table-column :prop="items.prop" :label="items.label">
                </el-table-column>
              </div>
            </el-table-column>
        </template>