#模块
plUI <- function(id) {
  tagList(
    selectInput(NS(id, "var"), "变量", choices = names(mtcars)),
    numericInput(NS(id, "bins"), "柱数", value = 10, min = 1),
    plotOutput(NS(id, "hist"), click = "plot_click"),
    verbatimTextOutput("info")
  )
}
plServer <- function(id) {
  moduleServer(id, function(input, output, session) {
    data <- reactive(mtcars[[input$var]])
    output$hist <- renderPlot({
      plot(data(), breaks = input$bins, main = input$var)
    }, res = 96)
    output$info <- renderPrint({
      req(input$plot_click)
      x <- round(input$plot_click$x, 2)
      y <- round(input$plot_click$y, 2)
      cat("[", x, ", ", y, "]", sep = "")
    })
    
  })
}
#------------------------------用户界面(UI)-------------------------------------
ui <- fluidPage(
  plUI("p1")
)
#------------------------------服务器端(Server)-------------------------------------
server <- function(input, output, session) {
  plServer("p1")
}
shinyApp(ui, server)

library(shiny)
plUI <- function(id) {
  ns <- NS(id)
  tagList(
    selectInput(ns("var"), "Variable", choices = names(mtcars)),
    numericInput(ns("bins"), "bins", value = 10, min = 1),
    plotOutput(ns("hist"), click = ns("plot_click")),
    verbatimTextOutput(ns("info"))
  )
}
plServer <- function(id) {
  moduleServer(id, function(input, output, session) {
    ns <- session$ns
    
    data <- reactive(mtcars[[input$var]])
    
    output$hist <- renderPlot({
      plot(data(), breaks = input$bins, main = input$var)
    }, res = 96)
    
    output$info <- renderPrint({
      req(input$plot_click)
      x <- round(input$plot_click$x, 2)
      y <- round(input$plot_click$y, 2)
      cat("[", x, ", ", y, "]", sep = "")
    })
  })
}
#------------------------------UI-------------------------------------
ui <- fluidPage(
    plUI("p1")
)
#------------------------------SERVER-------------------------------------
server <- function(input, output, session) {
  plServer("p1")
}
shinyApp(ui, server)

<details>
<summary>英文:</summary>
- Instead of `NS(id, &quot;var&quot;)` for each id, you can do `ns &lt;- NS(id)` and then use `ns(&quot;var&quot;)` and so on. 
- `plot_click` is also an id so wrap it in `ns` as well. 
- You had forgotten `NS` in `verbatimTextOutput(&quot;info&quot;)`. 
- The main `ui` had two `fluidPage` that probably was by mistake so removed it. 

data <- reactive(mtcars[[input$var]])
output$hist <- renderPlot({
  plot(data(), breaks = input$bins, main = input$var)
}, res = 96)
output$info <- renderPrint({
  req(input$plot_click)
  x <- round(input$plot_click$x, 2)
  y <- round(input$plot_click$y, 2)
  cat("[", x, ", ", y, "]", sep = "")
})

[![enter image description here][1]][1]
  [1]: https://i.stack.imgur.com/PN78R.gif
</details>