How to create mysql database table in magento 2

whats wrong in my install file? InstallSchema.php

public function install(\Magento\Framework\Setup\SchemaSetupInterface $setup, \Magento\Framework\Setup\ModuleContextInterface $context)
{


    $installer = $setup;
    $installer->startSetup();
    if (!$installer->tableExists('tbl_crud_items')) {
        $table = $installer->getConnection()->newTable(
            $installer->getTable('tbl_crud_items')
        )
            ->addColumn(
                'item_id',
                \Magento\Framework\DB\Ddl\Table::TYPE_INTEGER,
                null,
                [
                    'identity' => true,
                    'nullable' => false,
                    'primary'  => true,
                    'unsigned' => true,
                ],
                'Item ID'
            )
            ->addColumn(
                'name',
                \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
                255,
                ['nullable => false'],
                'Item Name'
            )
            ->addColumn(
                'post_content',
                \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
                '64k',
                [],
                'Item Content'
            )
            ->addColumn(
                'status',
                \Magento\Framework\DB\Ddl\Table::TYPE_INTEGER,
                1,
                [],
                'Item Status'
            )
            ->addColumn(
                'featured_image',
                \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
                255,
                [],
                'Item Featured Image'
            )
            ->addColumn(
                'created_at',
                \Magento\Framework\DB\Ddl\Table::TYPE_TIMESTAMP,
                null,
                ['nullable' => false, 'default' => \Magento\Framework\DB\Ddl\Table::TIMESTAMP_INIT],
                'Created At'
            )->addColumn(
                'updated_at',
                \Magento\Framework\DB\Ddl\Table::TYPE_TIMESTAMP,
                null,
                ['nullable' => false, 'default' => \Magento\Framework\DB\Ddl\Table::TIMESTAMP_INIT_UPDATE],
                'Updated At')
            ->setComment('Item Table');
        $installer->getConnection()->createTable($table);

        $installer->getConnection()->addIndex(
            $installer->getTable('tbl_crud_items'),
            $setup->getIdxName(
                $installer->getTable('tbl_crud_items'),
                ['name', 'post_content', 'featured_image'],
                \Magento\Framework\DB\Adapter\AdapterInterface::INDEX_TYPE_FULLTEXT
            ),
            ['name', 'post_content','featured_image'],
            \Magento\Framework\DB\Adapter\AdapterInterface::INDEX_TYPE_FULLTEXT
        );
    }
    $installer->endSetup();
}