Why does Nginx drop gRPC connection when load testing through Locust after a while? How to fix?

Question

Python

*23735 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 172.22.0.4, server: , request: "POST /SpeechToTextService/StreamingRecognize HTTP/2.0", upstream: " grpc://172.22. 0.2:8119 ", host: " nginx:8558 "

What is the correct way to make sure that the connection is not dropped or terminated when I think the request is completed? I understand that nginx holds the connection between containers for a while.

http {
    fastcgi_read_timeout 300;
    proxy_read_timeout 300;
    uwsgi_read_timeout 300;
}

server {
    listen 8558 http2;
    charset utf-8;
    location / {
        grpc_pass grpc://stt:8119;
    }
}