use await in foreach

foreach_await.js

async function Process(source, signature) {
    const unspents = [1];
    return new Promise((resolve, reject) => {
        const len = unspents.length;
        asyncForEach(unspents, async (k) => {
            const encode = await sleepFunc(source)
            if (!encode) {
                reject()
            }
            if (k === (len-1)) {
                // todo
                resolve(signature+'xx');
            }
        })
        
    });

}

async function sleepFunc(source) {
    return new Promise((resolve, reject) => {
    setTimeout(() => {
            resolve(source);
        },3000);
    })
}

async function asyncForEach(array, callback) {
  for (let index = 0; index < array.length; index++) {
    await callback(index)
  }
}