grpc keepalive does not effect, nginx will close connection by the minute

[Roar]

Thanks Sergey Kandaurov. 
The second problem is that I set grpc_read_timeout and grpc_send_timeout but
it seems does not take effect. I tested many times and found that if the
read_timeout less than default 60s, then it works. But it has no effect when
read_timeout more than 60s, nginx will automatically close the connection
between nginx and grpc server by every 60s. How to configure parameters to
fix this issue?

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,282769,282788#msg-282788