异步/等待promise。所有转换问题

Question

我有以下代码可在异步功能中使用，但是正在串行运行。

const streamPromise = stream => new Promise((res, rej) => {
    stream.on( 'end', () => res('end') );
    stream.on( 'finish', () => res( stream.read() ) );
    stream.on( 'error', e => rej(e) );
});

for (var obj of lookupMd5) {
    console.log(`Working on ${obj}`);
    const hash = crypto
            .createHash('md5')
            .setEncoding('hex');
    const readStream = s3.getObject({Bucket: bucket, Key: obj}).createReadStream();
    readStream.on('error', err => {
        console.error('s3 download error', err);
        hash.emit('error', err);
    });
    readStream.pipe(hash);

    const md5 = await streamPromise(hash);
    console.log('md5', md5);

    haveMd5.push( { Key: obj.replace(prefix, ''), Md5: md5 } );
}

想使用类似的东西转换为并行运行的代码

const streamPromise = stream =>
    new Promise((res, rej) => {
        stream.on('end', () => res('end'));
        stream.on('finish', () => res(stream.read()));
        stream.on('error', e => rej(e));
    });

const md5s = Promise.all(
    lookupMd5.map(obj => {
        console.log(`Working on ${obj}`);
        const hash = crypto.createHash('md5').setEncoding('hex');
        const readStream = s3.getObject({ Bucket: bucket, Key: obj }).createReadStream();
        readStream.on('error', err => {
            console.error('s3 download error', err);
            hash.emit('error', err);
        });
        readStream.pipe(hash);

        return { Key: obj.replace(prefix, ''), Md5: await streamPromise(hash) };
    })
);
console.log('md5s', JSON.stringify(md5s, null, 2));

但是在Md5: await streamPromise(hash)的对象中得到了意外的令牌'streamPromise'。

如果我更改为

，则在同一位置出现意外令牌'streamPromise'

const streamPromise = async stream => {
    stream.on( 'end', () => 'end' );
    stream.on('finish', () => stream.read());
    stream.on('error', e => { throw e });
};

const md5s = Promise.all(
    lookupMd5.map(obj => {
        console.log(`Working on ${obj}`);
        const hash = crypto.createHash('md5').setEncoding('hex');
        const readStream = s3.getObject({ Bucket: bucket, Key: obj }).createReadStream();
        readStream.on('error', err => {
            console.error('s3 download error', err);
            hash.emit('error', err);
        });
        readStream.pipe(hash);

        return { Key: obj.replace(prefix, ''), Md5: await streamPromise(hash) };
    })
);

console.log('md5s', JSON.stringify(md5s, null, 2));