I am new to the concept of containerising R shiny apps using Docker and I was trying to deploy my R shiny application on Azure cloud environment by deploying a docker container image. This R shiny app tries to connect to a PostgreSQL DB which has already been setup on Azure cloud environment. So in order to connect R shiny app to cloud based PostgreSQL DB, I am trying to install RPostgres,RPostgreSQL and DBI packages for establishing the connection, in my docker image.