How do I have variable file inputs for a Shiny app in R?

My shiny app requires users to input a file they want to process, but I would also like to provide an option to use the default file for them to try out the dashboard. I've set up a radio button to use that file in my ui.R like so:

checkboxInput("checkbox", label = "Or Use default file", value = FALSE)

In my server.R, I have defined the logic as follows:

# Define server logic to read selected file ----
server <- function(input, output) {
    output$myTable <- renderDataTable({
        
        # input$file1 will be NULL initially. After the user selects
        # and uploads a file, head of that data file by default,
        # or all rows if selected, will be shown.
        if(input$checkbox == FALSE){
        req(input$file1)
   
       
        data <- readr::read_fwf(input$file1$datapath,
                       fwf_empty(input$file1$datapath),
                       skip = input$skiplines
        )}
        else {
            data <- readr::read_fwf("https://raw.githubusercontent.com/thedivtagguy/srishtilibrary/main/books_raw.txt", fwf_empty("https://raw.githubusercontent.com/thedivtagguy/srishtilibrary/main/books_raw.txt", col_names = c("Title")),skip = 10
            )
        }
        data <- data %>% rename(Title = X1)
 
        # Code to process the rest of the file follows
            return(data)}
} 

}

But this does not read the url of the text file and assign it to data when clicked. What am I doing wrong?

Full gist uploaded here: https://gist.github.com/thedivtagguy/74de5ae9d853828530f3414e6b52df95