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.

	if t.Proxy == nil || isDefault(t.Proxy) {
		// http.ProxyFromEnvironment doesn't respect CIDRs and that makes it impossible to exclude things like pod and service IPs from proxy settings
		// ProxierWithNoProxyCIDR allows CIDR rules in NO_PROXY
		t.Proxy = NewProxierWithNoProxyCIDR(http.ProxyFromEnvironment)
	}
	// If no custom dialer is set, use the default context dialer

		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"

		}

		config := &tls.Config{
			ServerName: u.Hostname(),
			RootCAs:    caCertPool,
			MinVersion: tls.VersionTLS12,
		}

		httpClient.Transport = &http.Transport{
			Proxy:           http.ProxyFromEnvironment,
			TLSClientConfig: config,
			DialContext: (&net.Dialer{
				Timeout: time.Second * 10,
			}).DialContext,
			IdleConnTimeout:       90 * time.Second,
			TLSHandshakeTimeout:   10 * time.Second,

	return sha256Sum, releaseTime, releaseInfo, err
}

func getUpdateTransport(timeout time.Duration) http.RoundTripper {
	var updateTransport http.RoundTripper = &http.Transport{
		Proxy:                 http.ProxyFromEnvironment,
		DialContext:           xhttp.NewInternodeDialContext(timeout, globalTCPOptions),
		IdleConnTimeout:       timeout,
		TLSHandshakeTimeout:   timeout,
		ExpectContinueTimeout: timeout,

			// never performed.
			caPool := x509.NewCertPool()
			require.True(t, caPool.AppendCertsFromPEM(caCert))

			client := &http.Client{
				Transport: &http.Transport{
					Proxy: http.ProxyFromEnvironment,
					TLSClientConfig: &tls.Config{
						RootCAs: caPool,
					},
				},
			}

			_, err = client.Transport.RoundTrip(req)

			if sha1checker.CheckRoundTripError(err) {

		responder   *fakeResponder
		expectedErr = errors.New("EXPECTED")
	)
	proxy := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		transport := &http.Transport{
			Proxy: http.ProxyFromEnvironment,
			DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
				return &fakeConn{err: expectedErr}, nil
			},
			MaxIdleConns:          100,
			IdleConnTimeout:       90 * time.Second,