Would be very handy to be able to connect to a running container from within a withRun block. I'm thinking it would behave exactly like inside(), except that it would run docker exec to run a command in the container. For example, if you needed to run a Postgres server with an extension installed, you could do it something like this:

script {
    image('postgres:10').withRun('-p 5432:5432') { c ->
        c.inside {
            // Attached to the Postgres container.
            sh "apt-get update"
            sh "apt-get install hypopg"
        }
        // Do stuff that relies on Postgres with hypopg
    }
}

I would think there would be plenty of use cases for spinning up a container and doing a bit of configuration on it before using a service it provides.

(Dupe GitHub Issue)