t.Fatalf("unexpected err: %v", err)
	}
	proxy, err := http.ProxyFromEnvironment(req)
	if err != nil {
		t.Fatalf("unexpected err: %v", err)
	}
	if proxy == nil {
		t.Skip("test skipped as ProxyFromEnvironment already initialized in environment without defined HTTP proxy")
	}
	t.Log("http.ProxyFromEnvironment is usable, continue executing test")
}

func TestKubeletVersionCheck(t *testing.T) {

	conn net.Conn

	// Dialer is the dialer used to connect.  Used if non-nil.
	Dialer *net.Dialer

	// proxier knows which proxy to use given a request, defaults to http.ProxyFromEnvironment
	// Used primarily for mocking the proxy discovery in tests.
	proxier func(req *http.Request) (*url.URL, error)

	// pingPeriod is a period for sending Ping frames over established
	// connections.

	}

	// For more details about various values used here refer
	// https://golang.org/pkg/net/http/#Transport documentation
	tr := &http.Transport{
		Proxy:                 http.ProxyFromEnvironment,
		DialContext:           dialContext,
		MaxIdleConnsPerHost:   maxIdleConnsPerHost,
		WriteBufferSize:       WriteBufferSize,
		ReadBufferSize:        ReadBufferSize,
		IdleConnTimeout:       15 * time.Second,

		// modified.
		r := *req
		*r.URL = *req.URL
		req = &r
		tlsConfig.InsecureSkipVerify = true
		req.URL.Scheme = "https"
	}

	transport := http.Transport{
		Proxy:           http.ProxyFromEnvironment,
		TLSClientConfig: tlsConfig,
	}

	return transport.RoundTrip(req)

	}

	args := &OperatorDNS{
		Endpoint: endpoint,
	}
	for _, setter := range setters {
		setter(args)
	}
	args.httpClient = &http.Client{
		Transport: &http.Transport{
			Proxy: http.ProxyFromEnvironment,
			DialContext: (&net.Dialer{
				Timeout:   3 * time.Second,
				KeepAlive: 5 * time.Second,
			}).DialContext,
			ResponseHeaderTimeout: 3 * time.Second,
			TLSHandshakeTimeout:   3 * time.Second,

			checkNewCertificateAndRotate()
			return hasCert.Load(), nil
		}, stopCh)
	}

	clientConfig.Transport = utilnet.SetTransportDefaults(&http.Transport{
		Proxy:               http.ProxyFromEnvironment,
		TLSHandshakeTimeout: 10 * time.Second,
		TLSClientConfig:     tlsConfig,
		MaxIdleConnsPerHost: 25,
		DialContext:         d.DialContext,
	})

// or might be using self-signed certificates.
var impatientInsecureHTTPClient = &http.Client{
	CheckRedirect: checkRedirect,
	Timeout:       5 * time.Second,
	Transport: &http.Transport{
		Proxy: http.ProxyFromEnvironment,
		TLSClientConfig: &tls.Config{
			InsecureSkipVerify: true,
		},
	},
}

var securityPreservingDefaultClient = securityPreservingHTTPClient(http.DefaultClient)

		refreshIntervalOnFailure: refreshIntervalOnFailure,
		retryInterval:            retryInterval,
		httpClient: &http.Client{
			Transport: &http.Transport{
				Proxy:             http.ProxyFromEnvironment,
				DisableKeepAlives: true,
			},
		},
	}

	caCertPool, err := x509.SystemCertPool()
	caCertsFound := true
	if err != nil {
		caCertsFound = false

// license that can be found in the LICENSE file.

// Package httpproxy provides support for HTTP proxy determination
// based on environment variables, as provided by net/http's
// ProxyFromEnvironment function.
//
// The API is not subject to the Go 1 compatibility promise and may change at
// any time.
package httpproxy

import (
	"errors"
	"fmt"
	"net"
	"net/url"
	"os"
	"strings"

		}
		url.Scheme = "https"
		source = url.String()
	}

	client := &http.Client{
		Transport: &http.Transport{
			ResponseHeaderTimeout: timeout + 5*time.Second,
			Proxy:                 http.ProxyFromEnvironment,
			TLSClientConfig:       tlsConfig,
		},
	}
	resp, err := client.Get(source)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {