Embed weather iframe into Shiny Dashboard - r

Question

I am trying to embed the weather forecast from forecast.io in a Shiny dashboard. I originally had trouble with the ampersand but saw a post that provided an example of how to format HTML code with special characters. However, when I run the app I see a simple "Not Found", even though I know that the link works and is being formatted correctly. I'm not sure what I'm missing.
library(shiny)
library(shinydashboard)
ui <- dashboardPage(
dashboardHeader(title = "Dashboard"),
dashboardSidebar(
sidebarMenu(
menuItem("Dashboard", tabName = "dashboard", icon = icon("dashboard"))
)
),
dashboardBody(
tabItems(
# First tab content
tabItem(tabName = "dashboard",
fluidRow(
column(12,
mainPanel(htmlOutput("frame")
)
)
)
)
)
)
)
server <- shinyServer(function(input, output) {
output$frame <- renderUI({
tags$iframe(id = 'app', src = url("https://forecast.io/embed/#lat=42.3583&lon=-71.0603&name=Downtown Boston"), width = '100%')
})
})
shinyApp(ui,server)
Screen capture of error in Shiny Dashboard

Answer 1

Update with inserted dashboard
I transfered url from server to ui:
library(shiny)
library(shinydashboard)
ui <- dashboardPage(
dashboardHeader(title = "Dashboard"),
dashboardSidebar(
sidebarMenu(
menuItem("Dashboard",
tabName = "dashboard",
icon = icon("dashboard")
)
)
),
dashboardBody(
tabItems(
tabItem(
tabName = "dashboard",
fluidRow(
tags$iframe(
seamless = "seamless",
src = "https://forecast.io/embed/#lat=42.3583&lon=-71.0603&name=Downtown Boston",
height = 800, width = 1400
)
)
)
)
)
)
server <- function(input, output) {}
shinyApp(ui, server)