Grpc server is sitting at my backends, I use nginx as the proxy to transfer http1.1 to http2(grpc) protocol, I set parameter like below:

upstream ID_PUMPER {
server 127.0.0.1:58548;
}

server {
listen 8080 http2;
grpc_read_timeout 120s;
grpc_send_timeout 120s;
grpc_socket_keepalive on;
keepalive_timeout 100s;

location /utoProto.idProduce.IdProduce {
grpc_pass grpc://ID_PUMPER;
}
}

It will establish connection between nginx and grpc server, but it can not hold the connection and the collection will be closed after one minute even though I set keepalive_timeout parameter, I found that nginx will send FIN packet to grpc server by monitoring the network packets through wireshark. How can I hold the connection but not close it by every minute?