code: func Handler() http.Handler {
  	return InstrumentMetricHandler(
  		prometheus.DefaultRegisterer, HandlerFor(prometheus.DefaultGatherer, HandlerOpts{}),
  	)
  }
docs: // Handler returns an http.Handler for the prometheus.DefaultGatherer, using
  // default HandlerOpts, i.e. it reports the first error as an HTTP error, it has
  // no error logging, and it applies compression if requested by the client.
  //
  // The returned http.Handler is already instrumented using the
  // InstrumentMetricHandler function and the prometheus.DefaultRegisterer. If you
  // create multiple http.Handlers by separate calls of the Handler function, the
  // metrics used for instrumentation will be shared between them, providing
  // global scrape counts.
  //
  // This function is meant to cover the bulk of basic use cases. If you are doing
  // anything that requires more customization (including using a non-default
  // Gatherer, different instrumentation, and non-default HandlerOpts), use the
  // HandlerFor function. See there for details.