If you are referring to the First Network example, you can see the volume mapping in CLI container (extracted from docker-compose-cli.yaml).

volumes:
        - /var/run/:/host/var/run/
        - ./../chaincode/:/opt/gopath/src/github.com/chaincode
        - ./crypto-config:/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/
        - ./scripts:/opt/gopath/src/github.com/hyperledger/fabric/peer/scripts/
        - ./channel-artifacts:/opt/gopath/src/github.com/hyperledger/fabric/peer/channel-artifacts

From which the fabric-samples/chaincode directory in your localhost is mapped to /opt/gopath/src/github.com/chaincodeinside CLI. You should be able to see this directory in CLI. Try go into the CLI container and check the file system.

docker exec -it cli bash

The good thing is that it’s a volume mapping. Anything you modify in fabric-samples/chaincode in your localhost host you will see it inside the CLI container.

Hope this helps.

kc