How can I pass reactive value into DiagrammeR::grViz()?

Question

I am trying to pass two reactive values into my Diagrammer::grViz code like [1]: paste0("Count is : \n", df()$count[rownum()]) where df() is my dataframe and rownum() is a specific selected row number.

I am getting error like 'df() not found' or 'rownum() not found'. I suppose that this error is coming because the whole grViz code inside the inverted commas.

Also \n is not working inside paste0().

Is there any solution to this?

Thanks in advance.

Example code below :

library(shiny)

app <- shinyApp(
  ui = fluidPage(
    
    DT::dataTableOutput("mydatatable")
  ),
  
  
  server =  shinyServer(function(input, output, session) {
    
    mycars <- reactive({ head(mtcars)})
    output$mydatatable = DT::renderDataTable(mycars(), selection = 'single',  
                                             rownames = FALSE, options = list(dom = 't'))
    selected_row <- reactiveVal(value = NULL)
    observeEvent(input$mydatatable_rows_selected,{
      selected_row(input$mydatatable_rows_selected)
    })
    
    observeEvent(selected_row(),
                 {
                   showModal(modalDialog(
                     title = "You have selected a row!",
                     DiagrammeR::grViz("
                                       digraph flowchart {
                                       graph [layout = dot]
                                       node [shape = rectangle, width = 3, fillcolor = Biege]
                                       a [label = '@@1']
                                       b [label = '@@2']
                                       
                                       a -> b
                                       }
                                       [1]: paste0('mpg = \n', mycars()$mpg[selected_row()])
                                       [2]: paste0('cyl = \n', mycars()$cyl[selected_row()])
                                       ", width = 200)
                   ))
                 })
  })
)

app