msc {
  a [label = "serviced"],
  b [label = "service"],
  c [label = "gorilla/mux"];

  a => b [label="NewRouter()"];
  b => c [label="NewRouter()"];
  |||;
  b note b [label="Bind routes to handlers", textbgcolor="#ffffcc", linecolour="#d3d3d3"];
  |||;
  a <- b [label="return: *mux.Router"];

}