async/await实现简版红绿灯

通过 async/await 实现简化版的红绿灯

代码如下：

async function changeColor(color, duration) {
    inner.style.backgroundColor = color;
    await sleep(duration);
}
function sleep(duration) {
    return new Promise((resolve) => {
        setTimeout(resolve, duration);
    });
}
async function main() {
    while (true) { // 实现循环
        await changeColor("green", 2000);
        await changeColor("yellow", 2000);
        await changeColor("red", 2000);
    }
}