Go running on App Engine terminated by container exit (1)

Question

I have a Go app running on Google App Engine. From the logs, I find this error container exit (1). Occasionally, you will see the upstream prematurely closed connection while reading response header from upstream, client: error when the container has exited when you run the varlog/system together with the /var/log/nginx/error.log file as shown in the image.

Error file

We are running the standard environment on app.yaml.

runtime: go111
env: standard

I added a nginx.conf file

events {
  worker_connections 768;
}

http {
  sendfile on;
  tcp_nopush on;
  tcp_nodelay on;
  keepalive_timeout 650;
  keepalive_requests 10000;
  types_hash_max_size 2048;
  include /etc/nginx/mime.types;
  default_type application/octet-stream;

  # Logs will appear on the Google Developer's Console when logged to this
  # directory.
  access_log /var/log/app_engine/app.log;
  error_log /var/log/app_engine/app.log;

  gzip on;
  gzip_disable "msie6";

  server {
    # Google App Engine expects the runtime to serve HTTP traffic from
    # port 8080.
    listen 8080;
    root /usr/share/nginx/www;
    index index.html index.htm;
  }
}

That didn't stop nginx from restarting.

Anybody experienced this or have any idea what could it be?

Thanks in advance.