Injest logs as JSON in Container Optimized OS

I am able to injest logs to Google Log Viewer with the help of stackdriver logging agent from Container Optimized OS as JSON.

It injests logs as a value to message, but not as json payload with the default configuration

What I have tried?

I have changed the fluentd config in /etc/stackdriver/logging.config.d/fluentd-lakitu.conf to the following:

  @type tail
  format json
  path /var/lib/docker/containers/*/*.log
    @type json
  pos_file /var/log/google-fluentd/containers.log.pos
  tag reform_contain
  read_from_head true

But its unable to send logs to Log viewer

OS: Container Optimized OS cos-81-12871-1196-0

Source: Docker Questions