}

// AcquireNet acquires a semaphore token for a network operation.
func AcquireNet() (release func(), err error) {
	hasToken := false
	if n, ok := NetLimit(); ok {
		if n == 0 {
			return nil, fmt.Errorf("network disabled by %v=%v", NetLimitGodebug.Name(), NetLimitGodebug.Value())
		}
		netLimitSem <- struct{}{}
		hasToken = true
	}

	checker := new(netTokenChecker)
	runtime.SetFinalizer(checker, (*netTokenChecker).panicUnreleased)

	{"BAR, FOO, BAZ", "foo", true},
	{"foobar", "foo", false},
	{"barfoo ", "foo", false},
}

func TestHasToken(t *testing.T) {
	for _, tt := range hasTokenTests {
		if hasToken(tt.header, tt.token) != tt.want {
			t.Errorf("hasToken(%q, %q) = %v; want %v", tt.header, tt.token, !tt.want, tt.want)
		}
	}
}

func TestNilHeaderClone(t *testing.T) {
	t1 := Header(nil)
	t2 := t1.Clone()
	if t2 != nil {

// returned without modifications.
func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }

// hasToken reports whether token appears with v, ASCII
// case-insensitive, with space or comma boundaries.
// token must be all lowercase.
// v may contain mixed cased.
func hasToken(v, token string) bool {
	if len(token) > len(v) || token == "" {
		return false
	}
	if v == token {
		return true
	}

func (r *Request) expectsContinue() bool {
	return hasToken(r.Header.get("Expect"), "100-continue")
}

func (r *Request) wantsHttp10KeepAlive() bool {
	if r.ProtoMajor != 1 || r.ProtoMinor != 0 {
		return false
	}
	return hasToken(r.Header.get("Connection"), "keep-alive")
}

func (r *Request) wantsClose() bool {
	if r.Close {
		return true
	}
	return hasToken(r.Header.get("Connection"), "close")
}

			return false
		}
		return true
	}

	return false
}

func (t *transferWriter) writeHeader(w io.Writer, trace *httptrace.ClientTrace) error {
	if t.Close && !hasToken(t.Header.get("Connection"), "close") {
		if _, err := io.WriteString(w, "Connection: close\r\n"); err != nil {
			return err
		}
		if trace != nil && trace.WroteHeaderField != nil {

	// protocol switch response and if KeepAlives are not enabled.
	// See https://golang.org/issue/36381.
	delConnectionHeader := w.closeAfterReply &&
		(!keepAlivesEnabled || !hasToken(cw.header.get("Connection"), "close")) &&
		!isProtocolSwitchResponse(w.status, header)
	if delConnectionHeader {
		delHeader("Connection")
		if w.req.ProtoAtLeast(1, 1) {
			setHeader.connection = "close"

		// mtime precision, reject caching if a file was read that
		// is less than modTimeCutoff old.
		//
		// This is the same strategy used for hashing test inputs.
		// See hashOpen in cmd/go/internal/test/test.go for the
		// corresponding code.
		if info.ModTime().After(cutoff) {
			return cache.ActionID{}, ErrNotIndexed
		}

			}
			if a.Package.Root == "" || search.InDir(name, a.Package.Root) == "" {
				// Do not recheck files outside the module, GOPATH, or GOROOT root.
				break
			}
			fh, err := hashOpen(name)
			if err != nil {
				if cache.DebugTest {
					fmt.Fprintf(os.Stderr, "testcache: %s: input file %s: %s\n", a.Package.ImportPath, name, err)
				}
				return cache.ActionID{}, err
			}