问使用async/await获取SyntaxError

EN

module.exports = class {
    constructor(web3) {
        this.web3 = web3.constructor.name === 'Web3' ? web3 : { eth: web3 };
        this.checkedBlocks = {};
        this.savedBlocks = {};
        this.requests = 0;
    }
.
.
.
    async getEvery(duration, start, end, every = 1, after = true) {
        start = moment(start), end = moment(end);
        let current = start, dates = [];
        while (current.isSameOrBefore(end)) {
            dates.push(current.format());
            current.add(every, duration);
        }
        if (typeof this.firstBlock == 'undefined' || typeof this.latestBlock == 'undefined' || typeof this.blockTime == 'undefined') await this.getBoundaries();
        return await Promise.all(dates.map((date) => this.getDate(date, after)));
    }
.
.
.

const EthDater = require('ethereum-block-by-date');
const { ethers } = require('ethers');
const url = "node url";
const provider = new ethers.providers.WebSocketProvider(url);

const dater = new EthDater(
    provider
);

let blocks = await dater.getEvery('hours', '2018-11-15T00:00:00Z', '2018-11-22T00:00:00Z');

console.log(blocks);