Copy and paste into your .bashrc file to give a new docker subcommand 'docker bash'

docker_bash_command

docker() {
    if [[ "$1" == "shell" ]]; then
        if [[ "$2" == "" ]]; then
            echo "usage:  docker shell CONTAINER_ID"
        else
            command docker exec -ti $2 bash||sh
        fi
    else
        command docker "$@"
    fi
}