shinycssloaders doesn't work when deployed on shinyapps.io

Question

I have a app that works just fine without adding shinycssloaders package. But for some reason, after I added the package and added the lines (see below), it stopped working if I deploy it with shinyapps.io. The app runs fine locally, just wouldn't let me deploy it.

# load the library
library(shinycssloaders)

withSpinner(plotOutput("my_plot")) 
# if you have `%>%` loaded, you can do plotOutput("my_plot") %>% withSpinner()

The error message I'm getting in the log is attached down below, but I have package shinycssloaders, and I've tried downloading it from CRAN and github, but neither works.

2019-05-13T16:41:39.317482+00:00 shinyapps[890504]: Using pandoc at /opt/connect/ext/pandoc2
2019-05-13T16:41:39.538904+00:00 shinyapps[890504]: Listening on http://127.0.0.1:46817
2019-05-13T16:41:43.893648+00:00 shinyapps[890504]: Warning: Error in withSpinner: could not find function "withSpinner"
2019-05-13T16:41:43.908035+00:00 shinyapps[890504]:   68: div
2019-05-13T16:41:43.908036+00:00 shinyapps[890504]:   67: mainPanel
2019-05-13T16:41:43.908034+00:00 shinyapps[890504]:   69: tags$div
2019-05-13T16:41:43.908032+00:00 shinyapps[890504]:   70: tag

I'm sure this work because it is on their github page, but I'm not sure what I did wrong. Worst case scenario, I'll just get rid of it so it's not a huge issue, but it'd be cool if I can use it. Any help is appreciated!

EDIT So I attached a sample code, feel free try to deploy it, did't work for me. But works fine locally (since it's a sample app, the loading spinner is extremely quick, but you'd still be able to see it).

library(shiny)
library(shinycssloaders)

ui <- fluidPage(
  actionButton("go", "Go"),
  numericInput("n", "n", 50),
  withSpinner(plotOutput("my_plot"))
)

server <- function(input, output) {

  randomVals <- eventReactive(input$go, {
    runif(input$n)
  })

  output$my_plot <- renderPlot({
    hist(randomVals())
  })
}

shinyApp(ui, server)

Answer 1

Since the log says Warning: Error in withSpinner: could not find function "withSpinner" I went ahead added the package name in front of withSpinner function, so now in the UI function, it should be

shinycssloaders::withSpinner(plotOutput("my_plot", height = 600))

and it works perfect with deploy. Although it seems bizarre, because I indeed attached library(shinycssloaders). In my actual app, I attached it in server.R file, perhaps that's why.