Nginx CORS 'Access-Control-Allow-Origin' header - reactjs

Question

I have configured the Nginx reverse proxy with below configuration:
location ^~ /api/my-service/ {
if ($request_method = 'OPTIONS') {
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS, HEAD';
add_header 'Access-Control-Allow-Headers' 'Authorization,DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
add_header 'Access-Control-Max-Age' 1728000;
add_header 'Content-Type' 'text/plain; charset=utf-8';
add_header 'Content-Length' 0;
return 200;
}
if ($request_method = 'GET') {
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
add_header 'Access-Control-Allow-Headers' 'Authorization, DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range';
}
}
When this service is called from a different origin, in the network tab i see the response of a service like:
http://nginx-host/api/my-service/users/user
and the response headers are:
Cache-Control no-cache, no-store, max-age=0, must-revalidate
Connection keep-alive
Content-Type application/json;charset=UTF-8
Date Tue, 10 Apr 2018 07:54:40 GMT
Expires 0
Pragma no-cache
Server nginx/1.10.3 (Ubuntu)
Transfer-Encoding chunked
X-Content-Type-Options nosniff
X-Frame-Options DENY
X-XSS-Protection 1; mode=block
In the console of chrome/firefox i see:
Failed to load http://nginx-host/api/my-service/users/user: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://10.11.13.202:2200' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
This call is made from a react based application, shall i add something in the request headers as well in order to get this through.
The OPTIONS response has headers displayed properly:
HTTP/1.1 204 No Content
Access-Control-Allow-Headers: Authorization,DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range
Access-Control-Allow-Methods: GET, POST, OPTIONS, HEAD
Access-Control-Allow-Origin: *
Access-Control-Max-Age: 1728000
Connection: keep-alive
Content-Length: 0
Content-Type: text/plain; charset=utf-8
Date: Tue, 10 Apr 2018 08:08:53 GMT
Server: nginx/1.10.3 (Ubuntu)

Answer 1

The API exposed is cheeky, for a GET request the response header is 202 accepted which ideally should have been 200, NGINX in this case does not append the response headers and messes up the configurations. Duh!

Answer 2

Another way would be to use always alongside the * placeholder something like:
add_header 'Access-Control-Allow-Origin' '*' always;
works!