Passing reactive data as choices for updateSelectizeInput

I am trying to pass reactive data to updateSelectizeInput but instead get the following error :

Error in .getReactiveEnvironment()$currentContext() : Operation not allowed without an active reactive context. (You tried to do something that can only be done from inside a reactive expression or observer.)

My code is as follows :

ui.R

 library(shiny)  ui_panel <-   tabPanel("Text Input Test",          sidebarLayout(           sidebarPanel(            selectizeInput('Organisations', label = "Organisation Search",    choices = NULL, options = list(             placeholder = 'Type the organisation name', maxOptions = 10,    maxItems = 1, searchConjunction = 'and')),           tags$style(type="text/css",".selectize-input::after{visibility:hidden;};"                      ),           br(),           selectInput(             inputId="selectData",             label="",             choices=c("Universities", "Hospitals")           ),           br()         ),         mainPanel(           tabsetPanel(             tabPanel("output of Organisation search  details",htmlOutput("orgsearchdetails"))           )         )       ))ui <- shinyUI(navbarPage("",ui_panel))

server.R

   library(shiny)  shinyServer(   function(input, output, session) {    orgdata <- reactive({if(input$selectData=='Universities'){    orgdata <- read.csv("universities.csv")   }else if (input$selectData=='Hospitals'){     orgdata <- read.csv("hospitals.csv")    }    orgdata   })    updateSelectizeInput(session, 'Organisations', choices =    as.character(unique(     orgdata()$name)), server = TRUE)  output$orgsearchdetails <-renderUI({     })  session$onSessionEnded(function() { dbDisconnect(con) })  })

Is there a way I can pass the reactivity of the selectInput to the updateSelectizeInput ?

I am opting for updateSelectizeInput instead of a reactive selectInput so as to avoid populating the filed at the launch of the application.

Any help or insight is highly welcome. thank you in advance.