tabItem("chooseFile",
          fluidRow(
            box(
              width = 5, status = "info",solidHeader = TRUE,
              title = "Send Emails",
              helpText(tags$b("Please uplaod .csv or .tsv file")),
              tags$hr(),
              fileInput('csv_file', 'Choose file to upload',
                        accept = c(
                          'text/csv',
                          'text/comma-separated-values',
                          'text/tab-separated-values',
                          'text/plain',
                          '.csv',
                          '.tsv'
                        )
              ),
              tags$hr(),
              checkboxInput('header', 'Header', TRUE),
              radioButtons('sep', 'Separator',
                           c(Comma=',',
                             Semicolon=';',
                             Tab='t'),
                           ','),
              actionButton("upload_file", tags$b("Upload File"))


              )
            )
          ),

observeEvent(input$upload_file, {
     csv <- input$csv_file
     saveData(csv)
     session$sendCustomMessage(type ='testmessage',
                               message = paste0("File has been successfully uploaded to database"))

   })

saveData <- function(data) {
    # Connect to the database
    db <- dbConnect(MySQL(), dbname = databaseName, host = options()$mysql$host,
              port = options()$mysql$port, user = options()$mysql$user,
              password = options()$mysql$password)
    # Construct the update query by looping over the data fields
    dbWriteTable(db, table, input$csv, overwrite = TRUE)

    dbDisconnect(db)

    return(final_data)
  }

Error in dbWriteTable(db, table, input$csv_file, overwrite = TRUE) :
object 'input' not found