NightmareJS: how to set cookie?

var Nightmare = require('nightmare');
var nightmare = Nightmare({
    show: true
})

nightmare
    .goto('https://mail.yandex.ru')
    .type('input[name=login]', 'mylogin')
    .type('input[name=passwd]', 'mypassword')
    .click('button.nb-button._nb-action-button.nb-group-start')
    .wait('.mail-User-Name')
    .cookies.get()
    .then(function (cookies) {
        //actions
    })

I am getting cookies after authorization, but I don't know where I must set them and how I must set them. I've tried to do .cookie.set() at the beginning, but this doesn't work.

How I can use saved cookie? Thanks.

I did the following from the node terminal:

> var Nightmare = require('nightmare')
undefined
> var nightmare = Nightmare({show:true})
undefined
> nightmare.
... goto('https://google.com').
... cookies.set('foo', 'bar').
... cookies.get().
... then((cookies) => {
...     console.log(JSON.stringify(cookies, null, 4))
... })
Promise { <pending> }
> [
    {
    "name": "NID",
    "value": "96=qo1qY9LTKh1np4OSgiyJTi7e79-_OIoIuc71hnrKWvN1JUnDLJqZlE8u2ij_4mW0-JJhWOCafo5J0j-YkZCFt8H2VHzYUom4cfEd2QLOEsHmAcT2ACx4a5xSvO0SZGZp",
    "domain": ".google.de",
    "hostOnly": false,
    "path": "/",
    "secure": false,
    "httpOnly": true,
    "session": false,
    "expirationDate": 1502733434.077271
    },
    {
    "name": "CONSENT",
    "value": "WP.25d07b",
    "domain": ".google.de",
    "hostOnly": false,
    "path": "/",
    "secure": false,
    "httpOnly": false,
    "session": false,
    "expirationDate": 2145916800.077329
    },
    {
    "name": "foo",
    "value": "bar",
    "domain": "www.google.de",
    "hostOnly": true,
    "path": "/",
    "secure": false,
    "httpOnly": false,
    "session": true
    }
]

nightmare.cookies.set('key', 'value') is indeed the correct way to use it, as you can see in my result object. Perhaps https://mail.yandex.ru does not accept your cookie, because it's invalid. Please do the same and edit your question to include your results.

Edit: Apparently, OP needs to store the cookies so he can use them in another Nightmare instance. This can be achieved like this:

var Nightmare = require('nightmare')
var storedCookies // This is where we will store the cookies. It could be stored in a file or database to make it permanent

// First instance:
var nightmare1 = Nightmare({show: true})
nightmare1.
    goto('https://google.com').
    cookies.get().
    then((cookies) => {
        storedCookies = cookies
    })

// Second instance:
var nightmare2 = Nightmare({show: true})

for(var i = 0; i < storedCookies.length; i++)
    nightmare2.
        cookies.set(storedCookies[i].name, storedCookies[i].value)

nightmare2.
    goto('https://google.com')