Let's presuppose you don't have even a MySQL DB ready.
docker run --name iron-mysql -e MYSQL_ROOT_PASSWORD=root \
-e MYSQL_DATABASE=funcs -e MYSQL_USER=iron -e MYSQL_PASSWORD=ironfunctions -d mysql
For more configuration options, see docker mysql docs.
docker run --rm --privileged --link "iron-mysql:mysql" \
-e "DB_URL=mysql://iron:ironfunctions@tcp(mysql:3306)/funcs" \
-it -p 8080:8080 iron/functions