Elasticsearch + searchkit basicauth - getting 401 Unauthorized when contacting ES

Question

I am trying to secure my ES instance for use with searchkit.

I have nginx-proxied my ES instance to proxy port 9200 requests on port 8080 and enabled a basic authentication on top of that.

My server is correctly reachable from browser (http://admin:password@es_server_ip:8080 is correctly reaching ES Json) and authentication is working properly.

In order to set searchkit I followed this sample :

http://docs.searchkit.co/stable/setup/elasticsearch.html

and entered my server configuration constants to reach my server with authentication :

const host = "http://192.168.1.28:8080/index_test"
const searchkit = new SearchkitManager(host, { basicAuth:"admin:elastic" })

But it seems that searchkit is unable to reach my server and returning a 401/Unauthorized on every ES connection no matter what (I can clearly see it from browser console)

Note that I am correctly able to use searchkit without authentication.

Any idea on what is wrong ?