axios does not send POST to golang api

I have a golang api backend with a negroni middleware.

I already implemented the CORS handler for negroni, so my api should allow cross origin resource sharing.

// allow OPTIONS method of CORS requests
c := cors.New(cors.Options{
    AllowedOrigins: []string{"http://127.0.0.1"},
})

//common.StartUp() - Replaced with init method
// Get the mux router object
router := routers.InitRoutes()
// Create a negroni instance
n := negroni.Classic()
n.Use(c)
n.UseHandler(router)

server := &http.Server{
    Addr:    common.AppConfig.Server,
    Handler: n,
}
log.Println("Listening...")
server.ListenAndServe()

This is from the https://github.com/rs/cors/blob/master/examples/negroni/server.go example of implementing CORS with negroni.

Nevertheless my api now responses a 200 status back to my frontend, but the frontend does not send the POST request to the server. This my axios code:

import axios from 'axios';
const data = {
email: 'user@mail.com',
password: 'secret',
};

export default {
name: 'Login',
methods: {
login() {
  axios.post('https://127.0.0.1:8090/users/login', data);
},

Postman does not have any problems with sending the POST request. What am I doing wrong?

Okay I found a solution for the problem:

As described in this article, I added some more options to the cors negroni plugin. One important option that was missing in my application was the line

AllowedHeaders: []string{"X-Auth-Key", "X-Auth-Secret", "Content-Type"},

Because my app sent the Content-Type Header and the api refused it.

I hope this will help others with similar problems.