using textInput to define url to scrape from

My goal is an app that scrapes and maps html table data, by date. Each date has its own url with its yyyymmdd suffix, eg:

https://cdec.water.ca.gov/reportapp/javareports?name=PAGE6.20191219https://cdec.water.ca.gov/reportapp/javareports?name=PAGE6.20191216

The intention is for the user to enter the 8-digit date in a textInput field, and the app to build the url and scrape and map the data.

With what I have:

library(shiny)
library(leaflet)
library(shinyjs)
library(shinydashboard)
library(XML)

ui <- dashboardPage(
dashboardHeader(),
dashboardSidebar(

textInput("text", "by 8 digit yyyymmdd:", "20191216")),

dashboardBody(
tags$style(type = "text/css", "#mapplot {height: calc(100vh - 80px) !important;}"),
leafletOutput("mapplot"),
useShinyjs() ) )

server <- function(input, output) {
 addClass(selector = "body")
 options(shiny.maxRequestSize=225*1024^2)

baseurl <- "http://cdec.water.ca.gov/reportapp/javareports?name=PAGE6."

# append the user-entered yyyymmdd to the base url
url <- reactive({paste0(baseurl, input$text)})

# scrape data
cdec_swe_table  <- readHTMLTable(url)

# process data and display on map
# this part already works, it's defining the url from user input that I can't do

}

shinyApp(ui, server)

I get:

Error in (function (classes, fdef, mtable)  : 
unable to find an inherited method for function ‘readHTMLTable’ for 
signature ‘"reactiveExpr"’

I think I'm missing some reactivity fundamentals. Any help greatly appreciated.