Shiny readRDS fail to work with rds object containing a list of data frame

Question

I was trying to develop a shiny app that allows users to upload an rds file and do clustering analysis. The rds object contains a list of dataframe. Yet somehow the readRDS function didn't work with my rds object.

Here is part of my code

library(shiny)

ui <- fluidPage(

  # App title ----
  titlePanel("test"),

  sidebarLayout(
    wellPanel(
        fileInput(inputId = 'upload',NULL,
                    label= 'Upload an rds file',
                    buttonLabel = 'Choose File',multiple=FALSE,
                    placeholder = 'No file selected',
                    accept = '.rds'),
        
        mainPanel(
            tableOutput('content')
        
        )
    )          
  )
)

server <- function(input,output) {
    my_dtw <-reactive({
        file <-input$upload
        
        ext <- tools::file_ext(file$datapath)
        req(file)
    
        validate(need(ext == "rds", "Please upload a rds file"))

        df <-readRDS(file$datapath)
        return(df)
    })
    
    output$content <- renderTable(my_dtw()[1:3,])
    
    }

shinyApp(ui = ui, server = server)

And here is my rds object:https://github.com/JuanXie19/data/blob/main/Mice.sub2.trajectory.rds

Many thanks in advance!!