How can I insert data into db after auto install?

[me-kou]

Thanks for your docker-modx repository! it helps me a lot.

Now I want to source my mysql dump file after auto install in docker enviroment.
I was successful in command as follow, but I want to run it auto instead of manually..

mysql -u root -h 127.0.0.1 -P 13307 --protocol=tcp -p
password:
use modx;
source my.sql

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This is what I've tried

1. make a directory as 「docker-entrypoint-initdb.d」 in mariadb directory
2. put my mysql inside the 「docker-entrypoint-initdb.d」 directory.
3. edit Dockerfile inside mariadb as follow

FROM mariadb:10.1.38-bionic
COPY ./docker-entrypoint-initdb.d/ ./docker-entrypoint-initdb.d/

But it doesn't work..
What should I do so that I can insert my dump date into running container ?

I am looking forward to your reply! Thank you guy !