generator-asynchronous-sequential-iteration

var co = require('co');

let items = [1,2,3];

function* getResult(item) {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve(item * 2), 100);
    });
}

co(function* () {
    for(let item of items) {
        let itemResult = yield getResult(item);
        console.log(itemResult);
    }
});

Note: in this case you should not use infinite sequence generator instead of items array because for-of loop is synchronous.