diff --git a/prometheus/promhttp/instrument_client_1_8_test.go b/prometheus/promhttp/instrument_client_1_8_test.go

deleted file mode 100644

index 7e3f522..0000000

--- a/prometheus/promhttp/instrument_client_1_8_test.go

+++ /dev/null

@@ -1,195 +0,0 @@

-// Copyright 2017 The Prometheus Authors

-// Licensed under the Apache License, Version 2.0 (the "License");

-// you may not use this file except in compliance with the License.

-// You may obtain a copy of the License at

-//

-// http://www.apache.org/licenses/LICENSE-2.0

-//

-// Unless required by applicable law or agreed to in writing, software

-// distributed under the License is distributed on an "AS IS" BASIS,

-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

-// See the License for the specific language governing permissions and

-// limitations under the License.

-

-// +build go1.8

-

-package promhttp

-

-import (

-	"log"

-	"net/http"

-	"testing"

-	"time"

-

-	"github.com/prometheus/client_golang/prometheus"

-)

-

-func TestClientMiddlewareAPI(t *testing.T) {

-	client := http.DefaultClient

-	client.Timeout = 1 * time.Second

-

-	reg := prometheus.NewRegistry()

-

-	inFlightGauge := prometheus.NewGauge(prometheus.GaugeOpts{

-		Name: "client_in_flight_requests",

-		Help: "A gauge of in-flight requests for the wrapped client.",

-	})

-

-	counter := prometheus.NewCounterVec(

-		prometheus.CounterOpts{

-			Name: "client_api_requests_total",

-			Help: "A counter for requests from the wrapped client.",

-		},

-		[]string{"code", "method"},

-	)

-

-	dnsLatencyVec := prometheus.NewHistogramVec(

-		prometheus.HistogramOpts{

-			Name:    "dns_duration_seconds",

-			Help:    "Trace dns latency histogram.",

-			Buckets: []float64{.005, .01, .025, .05},

-		},

-		[]string{"event"},

-	)

-

-	tlsLatencyVec := prometheus.NewHistogramVec(

-		prometheus.HistogramOpts{

-			Name:    "tls_duration_seconds",

-			Help:    "Trace tls latency histogram.",

-			Buckets: []float64{.05, .1, .25, .5},

-		},

-		[]string{"event"},

-	)

-

-	histVec := prometheus.NewHistogramVec(

-		prometheus.HistogramOpts{

-			Name:    "request_duration_seconds",

-			Help:    "A histogram of request latencies.",

-			Buckets: prometheus.DefBuckets,

-		},

-		[]string{"method"},

-	)

-

-	reg.MustRegister(counter, tlsLatencyVec, dnsLatencyVec, histVec, inFlightGauge)

-

-	trace := &InstrumentTrace{

-		DNSStart: func(t float64) {

-			dnsLatencyVec.WithLabelValues("dns_start")

-		},

-		DNSDone: func(t float64) {

-			dnsLatencyVec.WithLabelValues("dns_done")

-		},

-		TLSHandshakeStart: func(t float64) {

-			tlsLatencyVec.WithLabelValues("tls_handshake_start")

-		},

-		TLSHandshakeDone: func(t float64) {

-			tlsLatencyVec.WithLabelValues("tls_handshake_done")

-		},

-	}

-

-	client.Transport = InstrumentRoundTripperInFlight(inFlightGauge,

-		InstrumentRoundTripperCounter(counter,

-			InstrumentRoundTripperTrace(trace,

-				InstrumentRoundTripperDuration(histVec, http.DefaultTransport),

-			),

-		),

-	)

-

-	resp, err := client.Get("http://google.com")

-	if err != nil {

-		t.Fatalf("%v", err)

-	}

-	defer resp.Body.Close()

-}

-

-func ExampleInstrumentRoundTripperDuration() {

-	client := http.DefaultClient

-	client.Timeout = 1 * time.Second

-

-	inFlightGauge := prometheus.NewGauge(prometheus.GaugeOpts{

-		Name: "client_in_flight_requests",

-		Help: "A gauge of in-flight requests for the wrapped client.",

-	})

-

-	counter := prometheus.NewCounterVec(

-		prometheus.CounterOpts{

-			Name: "client_api_requests_total",

-			Help: "A counter for requests from the wrapped client.",

-		},

-		[]string{"code", "method"},

-	)

-

-	// dnsLatencyVec uses custom buckets based on expected dns durations.

-	// It has an instance label "event", which is set in the

-	// DNSStart and DNSDonehook functions defined in the

-	// InstrumentTrace struct below.

-	dnsLatencyVec := prometheus.NewHistogramVec(

-		prometheus.HistogramOpts{

-			Name:    "dns_duration_seconds",

-			Help:    "Trace dns latency histogram.",

-			Buckets: []float64{.005, .01, .025, .05},

-		},

-		[]string{"event"},

-	)

-

-	// tlsLatencyVec uses custom buckets based on expected tls durations.

-	// It has an instance label "event", which is set in the

-	// TLSHandshakeStart and TLSHandshakeDone hook functions defined in the

-	// InstrumentTrace struct below.

-	tlsLatencyVec := prometheus.NewHistogramVec(

-		prometheus.HistogramOpts{

-			Name:    "tls_duration_seconds",

-			Help:    "Trace tls latency histogram.",

-			Buckets: []float64{.05, .1, .25, .5},

-		},

-		[]string{"event"},

-	)

-

-	// histVec has no labels, making it a zero-dimensional ObserverVec.

-	histVec := prometheus.NewHistogramVec(

-		prometheus.HistogramOpts{

-			Name:    "request_duration_seconds",

-			Help:    "A histogram of request latencies.",

-			Buckets: prometheus.DefBuckets,

-		},

-		[]string{},

-	)

-

-	// Register all of the metrics in the standard registry.

-	prometheus.MustRegister(counter, tlsLatencyVec, dnsLatencyVec, histVec, inFlightGauge)

-

-	// Define functions for the available httptrace.ClientTrace hook

-	// functions that we want to instrument.

-	trace := &InstrumentTrace{

-		DNSStart: func(t float64) {

-			dnsLatencyVec.WithLabelValues("dns_start")

-		},

-		DNSDone: func(t float64) {

-			dnsLatencyVec.WithLabelValues("dns_done")

-		},

-		TLSHandshakeStart: func(t float64) {

-			tlsLatencyVec.WithLabelValues("tls_handshake_start")

-		},

-		TLSHandshakeDone: func(t float64) {

-			tlsLatencyVec.WithLabelValues("tls_handshake_done")

-		},

-	}

-

-	// Wrap the default RoundTripper with middleware.

-	roundTripper := InstrumentRoundTripperInFlight(inFlightGauge,

-		InstrumentRoundTripperCounter(counter,

-			InstrumentRoundTripperTrace(trace,

-				InstrumentRoundTripperDuration(histVec, http.DefaultTransport),

-			),

-		),

-	)

-

-	// Set the RoundTripper on our client.

-	client.Transport = roundTripper

-

-	resp, err := client.Get("http://google.com")

-	if err != nil {

-		log.Printf("error: %v", err)

-	}

-	defer resp.Body.Close()

-}