(Nginx+Daphne+Django) Error during WebSocket handshake: Unexpected response code: 404 - django

Question

I have an Django(3.0) app using Daphne as an app container and Nginx as proxy server.
Daphne -u /home/ubuntu/virtualenvs/src/app/app.sock app.asgi:application
My problem is that the websocket connection failed.
(index):16 WebSocket connection to 'ws://example.com/ws/chat/1/' failed: Error during WebSocket handshake: Unexpected response code: 404
I'm pretty sure that my app setting and route is just fine.
Because if I stop Nginx, bind Daphne to 0.0.0.0:8000 and use real IP("ws://xx.xx.xx.xx:8000/ws/chat/1") as URL, the websocket connection established and very stable.
How should I modify my Nginx to make websocket work?
#my nginx setting
upstream websocket {
server unix:/home/ubuntu/virtualenvs/src/app/app.sock;
}
#websocket settings
map $http_upgrade $connection_upgrade {
default upgrade;
'' close;
}
server {
listen 80;
listen [::]:80 default_server;
listen 443 SSL default_server;
listen [::]:443 SSL default_server;
server_name example.com;
return 301 https://example.com$request_uri;
ssl on;
# certificate settings
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
ssl_session_timeout 10m;
#ssl_session cache shared:SSL:1m;
#ssl_protocols TLSv1 TLSv1.1 TLSv1.2 SSLv2 SSLv3;
#ssl_prefer_server_ciphers on;
#ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE:ECDH:AES:HIGH:!NULL:!aNULL:!$
location / {
root /home/ubuntu/virtualenvs/
include proxy_params;
proxy_pass https://websocket;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Frame-Options SAMEORIGIN;
proxy_pass_request_headers on;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
location ~* \.(js|css)$ {
expires -1;
}
}