Append logs using filebeat

My logs produce some content that I can see only when appended using (-A 20) or (- A 200). For Ex: While seeing a log from a docker container, I do :
docker logs [container_id] | grep "something" -A 20

Now i have implemnted ELK stack and collecting these logs using filebeats but the issue is I am unable to see those appended logs.

What should be done in the input section of filebeat.yml to get the appended result in kibana ?

filebeat.inputs:

-type: container
encoding: "utf-8"
paths:
- '/var/lib/docker/containers/ / .log'

It sounds like you're looking for Filebeat's multiline options: https://www.elastic.co/guide/en/beats/filebeat/current/multiline-examples.html.