function before(cb) {
waterfall(
f1,
f2,
cb
);
}
async function after() {
const r1 = await f1();
const r2 = await f2(r1);
return r2;
}
function before(cb) {
series(f1, f2, cb);
}
async function after() {
return [
await f1();
await f2();
];
}