title: How does one set global headers in axios?
body: <p>Hi I'm setting default axios headers in request interceptor but these headers are not accessible in another function... in axios <a href="https://github.com/mzabriskie/axios#global-axios-defaults" rel="noreferrer">axios documentation</a> it is mentioned that global-axios-defaults are global...below is my sample code need help</p>
  
  <pre><code>axios.interceptors.request.use(function (config) {
    axios.defaults.headers.accesstoken= "some_access_token"
    axios.defaults.headers.client = "some_client"
    axios.defaults.headers.uid = "some_uid"
    return config;
  },function (error) {
    return Promise.reject(error);
  });
  </code></pre>
  
  <p>On page load componentDidmount executes but axios default headers are undefined in this function</p>
  
  <pre><code>componentDidMount: function() {
    console.log(axios.defaults.headers) #its giving me undefined
    axios.get("http://some_url_for_get_request.json", {
      headers: {
        accesstoken: axios.defaults.headers.accesstoken,
         uid: axios.defaults.headers.uid,
         client: axios.defaults.headers.client
      }
    })
  }
  </code></pre>