Adding trace dynamically in plotly r shiny app

I am trying to add a plot in r shiny app using plotly. I can add it when I add the traces manually. But now I want to add the traces dynamically. Also I dont want to add traces for all columns. I just want to add traces for columns which end with sale. Below is the code so far. This doesnt even add all the traces. How can I add all the traces which just which have _sales in them.

output$pacingplot <- renderPlotly({
  colNames <- names(Delivery_data)[-1] #Assuming Date is the first column
  p <- plotly::plot_ly(x = ~Delivery_data$Date, type = "scatter",
                       mode = "lines")
  for(trace in colNames){
    p <- p %>% plotly::add_trace(y = as.formula(paste0("~`", trace, "`")), name = trace)
  p %>% 
    layout(title = "Impressions Over Time",
           xaxis = list(title = "Date"),
           yaxis = list (title = "Impressions"))

Below are the colnames (This doenst include date since I removed the first column):

[1] "apples_sales"           "apples_count"    "bananas_sales"          "bananas_count"   "oranges_sales"        "oranges_count" "peach_sales"          "peach_count"  

You may find an answers or some hints in this SO answer

Hope it helps