Unexpected token N in JSON at position 0 - node.js

Question

guys. I have a than error in my NodeJS rest API, and can't resolve this.
My idea is make a github login, this app working like this.
Href to github url returning a temporal code in callback.
Latter, send this temporal code to my REST API and with rest api make a fetch request to other endpoint of the github api, and this endpoint should return access_token=12345 (this access token is a example), for latter send this token to frontend, and convert the token in a JWT token and also send to frontend for latter storage in a localStorage to use it.
My code in NodeJS
router.post("/users/github/:code",function(req,res){
fetch('https://github.com/login/oauth/access_token/', {
method: 'GET',
client_id: 'xxxx',
client_secret: 'xxxx',
code: req.params.code,
accept: 'json',
})
.then(function(res) {
return res.json();
}).then(function(json) {
console.log(json);
});
});
PD: I use node-fetch module for this. https://www.npmjs.com/package/node-fetch

Answer 1

The solution
router.post("/users/github/:code",function(req,res){
fetch('https://github.com/login/oauth/access_token/', {
method: 'POST',
headers: {
Accept: 'application/json',
'Content-Type': 'application/json'
},
body: JSON.stringify({
client_id: 'xxxx',
client_secret: 'xxxx',
code: req.params.code
})
}).then(function(res) {
return res.json();
}).then(function(body) {
res.json(body);
});
});