diff --git a/vendor/golang.org/x/net/trace/trace.go b/vendor/golang.org/x/net/trace/trace.go
new file mode 100644
index 0000000..3ebf6f2
--- /dev/null
+++ b/vendor/golang.org/x/net/trace/trace.go
@@ -0,0 +1,1130 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package trace implements tracing of requests and long-lived objects.
+It exports HTTP interfaces on /debug/requests and /debug/events.
+
+A trace.Trace provides tracing for short-lived objects, usually requests.
+A request handler might be implemented like this:
+
+	func fooHandler(w http.ResponseWriter, req *http.Request) {
+		tr := trace.New("mypkg.Foo", req.URL.Path)
+		defer tr.Finish()
+		...
+		tr.LazyPrintf("some event %q happened", str)
+		...
+		if err := somethingImportant(); err != nil {
+			tr.LazyPrintf("somethingImportant failed: %v", err)
+			tr.SetError()
+		}
+	}
+
+The /debug/requests HTTP endpoint organizes the traces by family,
+errors, and duration.  It also provides histogram of request duration
+for each family.
+
+A trace.EventLog provides tracing for long-lived objects, such as RPC
+connections.
+
+	// A Fetcher fetches URL paths for a single domain.
+	type Fetcher struct {
+		domain string
+		events trace.EventLog
+	}
+
+	func NewFetcher(domain string) *Fetcher {
+		return &Fetcher{
+			domain,
+			trace.NewEventLog("mypkg.Fetcher", domain),
+		}
+	}
+
+	func (f *Fetcher) Fetch(path string) (string, error) {
+		resp, err := http.Get("http://" + f.domain + "/" + path)
+		if err != nil {
+			f.events.Errorf("Get(%q) = %v", path, err)
+			return "", err
+		}
+		f.events.Printf("Get(%q) = %s", path, resp.Status)
+		...
+	}
+
+	func (f *Fetcher) Close() error {
+		f.events.Finish()
+		return nil
+	}
+
+The /debug/events HTTP endpoint organizes the event logs by family and
+by time since the last error.  The expanded view displays recent log
+entries and the log's call stack.
+*/
+package trace // import "golang.org/x/net/trace"
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"html/template"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"net/url"
+	"runtime"
+	"sort"
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/net/internal/timeseries"
+)
+
+// DebugUseAfterFinish controls whether to debug uses of Trace values after finishing.
+// FOR DEBUGGING ONLY. This will slow down the program.
+var DebugUseAfterFinish = false
+
+// HTTP ServeMux paths.
+const (
+	debugRequestsPath = "/debug/requests"
+	debugEventsPath   = "/debug/events"
+)
+
+// AuthRequest determines whether a specific request is permitted to load the
+// /debug/requests or /debug/events pages.
+//
+// It returns two bools; the first indicates whether the page may be viewed at all,
+// and the second indicates whether sensitive events will be shown.
+//
+// AuthRequest may be replaced by a program to customize its authorization requirements.
+//
+// The default AuthRequest function returns (true, true) if and only if the request
+// comes from localhost/127.0.0.1/[::1].
+var AuthRequest = func(req *http.Request) (any, sensitive bool) {
+	// RemoteAddr is commonly in the form "IP" or "IP:port".
+	// If it is in the form "IP:port", split off the port.
+	host, _, err := net.SplitHostPort(req.RemoteAddr)
+	if err != nil {
+		host = req.RemoteAddr
+	}
+	switch host {
+	case "localhost", "127.0.0.1", "::1":
+		return true, true
+	default:
+		return false, false
+	}
+}
+
+func init() {
+	_, pat := http.DefaultServeMux.Handler(&http.Request{URL: &url.URL{Path: debugRequestsPath}})
+	if pat == debugRequestsPath {
+		panic("/debug/requests is already registered. You may have two independent copies of " +
+			"golang.org/x/net/trace in your binary, trying to maintain separate state. This may " +
+			"involve a vendored copy of golang.org/x/net/trace.")
+	}
+
+	// TODO(jbd): Serve Traces from /debug/traces in the future?
+	// There is no requirement for a request to be present to have traces.
+	http.HandleFunc(debugRequestsPath, Traces)
+	http.HandleFunc(debugEventsPath, Events)
+}
+
+// NewContext returns a copy of the parent context
+// and associates it with a Trace.
+func NewContext(ctx context.Context, tr Trace) context.Context {
+	return context.WithValue(ctx, contextKey, tr)
+}
+
+// FromContext returns the Trace bound to the context, if any.
+func FromContext(ctx context.Context) (tr Trace, ok bool) {
+	tr, ok = ctx.Value(contextKey).(Trace)
+	return
+}
+
+// Traces responds with traces from the program.
+// The package initialization registers it in http.DefaultServeMux
+// at /debug/requests.
+//
+// It performs authorization by running AuthRequest.
+func Traces(w http.ResponseWriter, req *http.Request) {
+	any, sensitive := AuthRequest(req)
+	if !any {
+		http.Error(w, "not allowed", http.StatusUnauthorized)
+		return
+	}
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	Render(w, req, sensitive)
+}
+
+// Events responds with a page of events collected by EventLogs.
+// The package initialization registers it in http.DefaultServeMux
+// at /debug/events.
+//
+// It performs authorization by running AuthRequest.
+func Events(w http.ResponseWriter, req *http.Request) {
+	any, sensitive := AuthRequest(req)
+	if !any {
+		http.Error(w, "not allowed", http.StatusUnauthorized)
+		return
+	}
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	RenderEvents(w, req, sensitive)
+}
+
+// Render renders the HTML page typically served at /debug/requests.
+// It does not do any auth checking. The request may be nil.
+//
+// Most users will use the Traces handler.
+func Render(w io.Writer, req *http.Request, sensitive bool) {
+	data := &struct {
+		Families         []string
+		ActiveTraceCount map[string]int
+		CompletedTraces  map[string]*family
+
+		// Set when a bucket has been selected.
+		Traces        traceList
+		Family        string
+		Bucket        int
+		Expanded      bool
+		Traced        bool
+		Active        bool
+		ShowSensitive bool // whether to show sensitive events
+
+		Histogram       template.HTML
+		HistogramWindow string // e.g. "last minute", "last hour", "all time"
+
+		// If non-zero, the set of traces is a partial set,
+		// and this is the total number.
+		Total int
+	}{
+		CompletedTraces: completedTraces,
+	}
+
+	data.ShowSensitive = sensitive
+	if req != nil {
+		// Allow show_sensitive=0 to force hiding of sensitive data for testing.
+		// This only goes one way; you can't use show_sensitive=1 to see things.
+		if req.FormValue("show_sensitive") == "0" {
+			data.ShowSensitive = false
+		}
+
+		if exp, err := strconv.ParseBool(req.FormValue("exp")); err == nil {
+			data.Expanded = exp
+		}
+		if exp, err := strconv.ParseBool(req.FormValue("rtraced")); err == nil {
+			data.Traced = exp
+		}
+	}
+
+	completedMu.RLock()
+	data.Families = make([]string, 0, len(completedTraces))
+	for fam := range completedTraces {
+		data.Families = append(data.Families, fam)
+	}
+	completedMu.RUnlock()
+	sort.Strings(data.Families)
+
+	// We are careful here to minimize the time spent locking activeMu,
+	// since that lock is required every time an RPC starts and finishes.
+	data.ActiveTraceCount = make(map[string]int, len(data.Families))
+	activeMu.RLock()
+	for fam, s := range activeTraces {
+		data.ActiveTraceCount[fam] = s.Len()
+	}
+	activeMu.RUnlock()
+
+	var ok bool
+	data.Family, data.Bucket, ok = parseArgs(req)
+	switch {
+	case !ok:
+		// No-op
+	case data.Bucket == -1:
+		data.Active = true
+		n := data.ActiveTraceCount[data.Family]
+		data.Traces = getActiveTraces(data.Family)
+		if len(data.Traces) < n {
+			data.Total = n
+		}
+	case data.Bucket < bucketsPerFamily:
+		if b := lookupBucket(data.Family, data.Bucket); b != nil {
+			data.Traces = b.Copy(data.Traced)
+		}
+	default:
+		if f := getFamily(data.Family, false); f != nil {
+			var obs timeseries.Observable
+			f.LatencyMu.RLock()
+			switch o := data.Bucket - bucketsPerFamily; o {
+			case 0:
+				obs = f.Latency.Minute()
+				data.HistogramWindow = "last minute"
+			case 1:
+				obs = f.Latency.Hour()
+				data.HistogramWindow = "last hour"
+			case 2:
+				obs = f.Latency.Total()
+				data.HistogramWindow = "all time"
+			}
+			f.LatencyMu.RUnlock()
+			if obs != nil {
+				data.Histogram = obs.(*histogram).html()
+			}
+		}
+	}
+
+	if data.Traces != nil {
+		defer data.Traces.Free()
+		sort.Sort(data.Traces)
+	}
+
+	completedMu.RLock()
+	defer completedMu.RUnlock()
+	if err := pageTmpl().ExecuteTemplate(w, "Page", data); err != nil {
+		log.Printf("net/trace: Failed executing template: %v", err)
+	}
+}
+
+func parseArgs(req *http.Request) (fam string, b int, ok bool) {
+	if req == nil {
+		return "", 0, false
+	}
+	fam, bStr := req.FormValue("fam"), req.FormValue("b")
+	if fam == "" || bStr == "" {
+		return "", 0, false
+	}
+	b, err := strconv.Atoi(bStr)
+	if err != nil || b < -1 {
+		return "", 0, false
+	}
+
+	return fam, b, true
+}
+
+func lookupBucket(fam string, b int) *traceBucket {
+	f := getFamily(fam, false)
+	if f == nil || b < 0 || b >= len(f.Buckets) {
+		return nil
+	}
+	return f.Buckets[b]
+}
+
+type contextKeyT string
+
+var contextKey = contextKeyT("golang.org/x/net/trace.Trace")
+
+// Trace represents an active request.
+type Trace interface {
+	// LazyLog adds x to the event log. It will be evaluated each time the
+	// /debug/requests page is rendered. Any memory referenced by x will be
+	// pinned until the trace is finished and later discarded.
+	LazyLog(x fmt.Stringer, sensitive bool)
+
+	// LazyPrintf evaluates its arguments with fmt.Sprintf each time the
+	// /debug/requests page is rendered. Any memory referenced by a will be
+	// pinned until the trace is finished and later discarded.
+	LazyPrintf(format string, a ...interface{})
+
+	// SetError declares that this trace resulted in an error.
+	SetError()
+
+	// SetRecycler sets a recycler for the trace.
+	// f will be called for each event passed to LazyLog at a time when
+	// it is no longer required, whether while the trace is still active
+	// and the event is discarded, or when a completed trace is discarded.
+	SetRecycler(f func(interface{}))
+
+	// SetTraceInfo sets the trace info for the trace.
+	// This is currently unused.
+	SetTraceInfo(traceID, spanID uint64)
+
+	// SetMaxEvents sets the maximum number of events that will be stored
+	// in the trace. This has no effect if any events have already been
+	// added to the trace.
+	SetMaxEvents(m int)
+
+	// Finish declares that this trace is complete.
+	// The trace should not be used after calling this method.
+	Finish()
+}
+
+type lazySprintf struct {
+	format string
+	a      []interface{}
+}
+
+func (l *lazySprintf) String() string {
+	return fmt.Sprintf(l.format, l.a...)
+}
+
+// New returns a new Trace with the specified family and title.
+func New(family, title string) Trace {
+	tr := newTrace()
+	tr.ref()
+	tr.Family, tr.Title = family, title
+	tr.Start = time.Now()
+	tr.maxEvents = maxEventsPerTrace
+	tr.events = tr.eventsBuf[:0]
+
+	activeMu.RLock()
+	s := activeTraces[tr.Family]
+	activeMu.RUnlock()
+	if s == nil {
+		activeMu.Lock()
+		s = activeTraces[tr.Family] // check again
+		if s == nil {
+			s = new(traceSet)
+			activeTraces[tr.Family] = s
+		}
+		activeMu.Unlock()
+	}
+	s.Add(tr)
+
+	// Trigger allocation of the completed trace structure for this family.
+	// This will cause the family to be present in the request page during
+	// the first trace of this family. We don't care about the return value,
+	// nor is there any need for this to run inline, so we execute it in its
+	// own goroutine, but only if the family isn't allocated yet.
+	completedMu.RLock()
+	if _, ok := completedTraces[tr.Family]; !ok {
+		go allocFamily(tr.Family)
+	}
+	completedMu.RUnlock()
+
+	return tr
+}
+
+func (tr *trace) Finish() {
+	elapsed := time.Now().Sub(tr.Start)
+	tr.mu.Lock()
+	tr.Elapsed = elapsed
+	tr.mu.Unlock()
+
+	if DebugUseAfterFinish {
+		buf := make([]byte, 4<<10) // 4 KB should be enough
+		n := runtime.Stack(buf, false)
+		tr.finishStack = buf[:n]
+	}
+
+	activeMu.RLock()
+	m := activeTraces[tr.Family]
+	activeMu.RUnlock()
+	m.Remove(tr)
+
+	f := getFamily(tr.Family, true)
+	tr.mu.RLock() // protects tr fields in Cond.match calls
+	for _, b := range f.Buckets {
+		if b.Cond.match(tr) {
+			b.Add(tr)
+		}
+	}
+	tr.mu.RUnlock()
+
+	// Add a sample of elapsed time as microseconds to the family's timeseries
+	h := new(histogram)
+	h.addMeasurement(elapsed.Nanoseconds() / 1e3)
+	f.LatencyMu.Lock()
+	f.Latency.Add(h)
+	f.LatencyMu.Unlock()
+
+	tr.unref() // matches ref in New
+}
+
+const (
+	bucketsPerFamily    = 9
+	tracesPerBucket     = 10
+	maxActiveTraces     = 20 // Maximum number of active traces to show.
+	maxEventsPerTrace   = 10
+	numHistogramBuckets = 38
+)
+
+var (
+	// The active traces.
+	activeMu     sync.RWMutex
+	activeTraces = make(map[string]*traceSet) // family -> traces
+
+	// Families of completed traces.
+	completedMu     sync.RWMutex
+	completedTraces = make(map[string]*family) // family -> traces
+)
+
+type traceSet struct {
+	mu sync.RWMutex
+	m  map[*trace]bool
+
+	// We could avoid the entire map scan in FirstN by having a slice of all the traces
+	// ordered by start time, and an index into that from the trace struct, with a periodic
+	// repack of the slice after enough traces finish; we could also use a skip list or similar.
+	// However, that would shift some of the expense from /debug/requests time to RPC time,
+	// which is probably the wrong trade-off.
+}
+
+func (ts *traceSet) Len() int {
+	ts.mu.RLock()
+	defer ts.mu.RUnlock()
+	return len(ts.m)
+}
+
+func (ts *traceSet) Add(tr *trace) {
+	ts.mu.Lock()
+	if ts.m == nil {
+		ts.m = make(map[*trace]bool)
+	}
+	ts.m[tr] = true
+	ts.mu.Unlock()
+}
+
+func (ts *traceSet) Remove(tr *trace) {
+	ts.mu.Lock()
+	delete(ts.m, tr)
+	ts.mu.Unlock()
+}
+
+// FirstN returns the first n traces ordered by time.
+func (ts *traceSet) FirstN(n int) traceList {
+	ts.mu.RLock()
+	defer ts.mu.RUnlock()
+
+	if n > len(ts.m) {
+		n = len(ts.m)
+	}
+	trl := make(traceList, 0, n)
+
+	// Fast path for when no selectivity is needed.
+	if n == len(ts.m) {
+		for tr := range ts.m {
+			tr.ref()
+			trl = append(trl, tr)
+		}
+		sort.Sort(trl)
+		return trl
+	}
+
+	// Pick the oldest n traces.
+	// This is inefficient. See the comment in the traceSet struct.
+	for tr := range ts.m {
+		// Put the first n traces into trl in the order they occur.
+		// When we have n, sort trl, and thereafter maintain its order.
+		if len(trl) < n {
+			tr.ref()
+			trl = append(trl, tr)
+			if len(trl) == n {
+				// This is guaranteed to happen exactly once during this loop.
+				sort.Sort(trl)
+			}
+			continue
+		}
+		if tr.Start.After(trl[n-1].Start) {
+			continue
+		}
+
+		// Find where to insert this one.
+		tr.ref()
+		i := sort.Search(n, func(i int) bool { return trl[i].Start.After(tr.Start) })
+		trl[n-1].unref()
+		copy(trl[i+1:], trl[i:])
+		trl[i] = tr
+	}
+
+	return trl
+}
+
+func getActiveTraces(fam string) traceList {
+	activeMu.RLock()
+	s := activeTraces[fam]
+	activeMu.RUnlock()
+	if s == nil {
+		return nil
+	}
+	return s.FirstN(maxActiveTraces)
+}
+
+func getFamily(fam string, allocNew bool) *family {
+	completedMu.RLock()
+	f := completedTraces[fam]
+	completedMu.RUnlock()
+	if f == nil && allocNew {
+		f = allocFamily(fam)
+	}
+	return f
+}
+
+func allocFamily(fam string) *family {
+	completedMu.Lock()
+	defer completedMu.Unlock()
+	f := completedTraces[fam]
+	if f == nil {
+		f = newFamily()
+		completedTraces[fam] = f
+	}
+	return f
+}
+
+// family represents a set of trace buckets and associated latency information.
+type family struct {
+	// traces may occur in multiple buckets.
+	Buckets [bucketsPerFamily]*traceBucket
+
+	// latency time series
+	LatencyMu sync.RWMutex
+	Latency   *timeseries.MinuteHourSeries
+}
+
+func newFamily() *family {
+	return &family{
+		Buckets: [bucketsPerFamily]*traceBucket{
+			{Cond: minCond(0)},
+			{Cond: minCond(50 * time.Millisecond)},
+			{Cond: minCond(100 * time.Millisecond)},
+			{Cond: minCond(200 * time.Millisecond)},
+			{Cond: minCond(500 * time.Millisecond)},
+			{Cond: minCond(1 * time.Second)},
+			{Cond: minCond(10 * time.Second)},
+			{Cond: minCond(100 * time.Second)},
+			{Cond: errorCond{}},
+		},
+		Latency: timeseries.NewMinuteHourSeries(func() timeseries.Observable { return new(histogram) }),
+	}
+}
+
+// traceBucket represents a size-capped bucket of historic traces,
+// along with a condition for a trace to belong to the bucket.
+type traceBucket struct {
+	Cond cond
+
+	// Ring buffer implementation of a fixed-size FIFO queue.
+	mu     sync.RWMutex
+	buf    [tracesPerBucket]*trace
+	start  int // < tracesPerBucket
+	length int // <= tracesPerBucket
+}
+
+func (b *traceBucket) Add(tr *trace) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	i := b.start + b.length
+	if i >= tracesPerBucket {
+		i -= tracesPerBucket
+	}
+	if b.length == tracesPerBucket {
+		// "Remove" an element from the bucket.
+		b.buf[i].unref()
+		b.start++
+		if b.start == tracesPerBucket {
+			b.start = 0
+		}
+	}
+	b.buf[i] = tr
+	if b.length < tracesPerBucket {
+		b.length++
+	}
+	tr.ref()
+}
+
+// Copy returns a copy of the traces in the bucket.
+// If tracedOnly is true, only the traces with trace information will be returned.
+// The logs will be ref'd before returning; the caller should call
+// the Free method when it is done with them.
+// TODO(dsymonds): keep track of traced requests in separate buckets.
+func (b *traceBucket) Copy(tracedOnly bool) traceList {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	trl := make(traceList, 0, b.length)
+	for i, x := 0, b.start; i < b.length; i++ {
+		tr := b.buf[x]
+		if !tracedOnly || tr.spanID != 0 {
+			tr.ref()
+			trl = append(trl, tr)
+		}
+		x++
+		if x == b.length {
+			x = 0
+		}
+	}
+	return trl
+}
+
+func (b *traceBucket) Empty() bool {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+	return b.length == 0
+}
+
+// cond represents a condition on a trace.
+type cond interface {
+	match(t *trace) bool
+	String() string
+}
+
+type minCond time.Duration
+
+func (m minCond) match(t *trace) bool { return t.Elapsed >= time.Duration(m) }
+func (m minCond) String() string      { return fmt.Sprintf("≥%gs", time.Duration(m).Seconds()) }
+
+type errorCond struct{}
+
+func (e errorCond) match(t *trace) bool { return t.IsError }
+func (e errorCond) String() string      { return "errors" }
+
+type traceList []*trace
+
+// Free calls unref on each element of the list.
+func (trl traceList) Free() {
+	for _, t := range trl {
+		t.unref()
+	}
+}
+
+// traceList may be sorted in reverse chronological order.
+func (trl traceList) Len() int           { return len(trl) }
+func (trl traceList) Less(i, j int) bool { return trl[i].Start.After(trl[j].Start) }
+func (trl traceList) Swap(i, j int)      { trl[i], trl[j] = trl[j], trl[i] }
+
+// An event is a timestamped log entry in a trace.
+type event struct {
+	When       time.Time
+	Elapsed    time.Duration // since previous event in trace
+	NewDay     bool          // whether this event is on a different day to the previous event
+	Recyclable bool          // whether this event was passed via LazyLog
+	Sensitive  bool          // whether this event contains sensitive information
+	What       interface{}   // string or fmt.Stringer
+}
+
+// WhenString returns a string representation of the elapsed time of the event.
+// It will include the date if midnight was crossed.
+func (e event) WhenString() string {
+	if e.NewDay {
+		return e.When.Format("2006/01/02 15:04:05.000000")
+	}
+	return e.When.Format("15:04:05.000000")
+}
+
+// discarded represents a number of discarded events.
+// It is stored as *discarded to make it easier to update in-place.
+type discarded int
+
+func (d *discarded) String() string {
+	return fmt.Sprintf("(%d events discarded)", int(*d))
+}
+
+// trace represents an active or complete request,
+// either sent or received by this program.
+type trace struct {
+	// Family is the top-level grouping of traces to which this belongs.
+	Family string
+
+	// Title is the title of this trace.
+	Title string
+
+	// Start time of the this trace.
+	Start time.Time
+
+	mu        sync.RWMutex
+	events    []event // Append-only sequence of events (modulo discards).
+	maxEvents int
+	recycler  func(interface{})
+	IsError   bool          // Whether this trace resulted in an error.
+	Elapsed   time.Duration // Elapsed time for this trace, zero while active.
+	traceID   uint64        // Trace information if non-zero.
+	spanID    uint64
+
+	refs int32     // how many buckets this is in
+	disc discarded // scratch space to avoid allocation
+
+	finishStack []byte // where finish was called, if DebugUseAfterFinish is set
+
+	eventsBuf [4]event // preallocated buffer in case we only log a few events
+}
+
+func (tr *trace) reset() {
+	// Clear all but the mutex. Mutexes may not be copied, even when unlocked.
+	tr.Family = ""
+	tr.Title = ""
+	tr.Start = time.Time{}
+
+	tr.mu.Lock()
+	tr.Elapsed = 0
+	tr.traceID = 0
+	tr.spanID = 0
+	tr.IsError = false
+	tr.maxEvents = 0
+	tr.events = nil
+	tr.recycler = nil
+	tr.mu.Unlock()
+
+	tr.refs = 0
+	tr.disc = 0
+	tr.finishStack = nil
+	for i := range tr.eventsBuf {
+		tr.eventsBuf[i] = event{}
+	}
+}
+
+// delta returns the elapsed time since the last event or the trace start,
+// and whether it spans midnight.
+// L >= tr.mu
+func (tr *trace) delta(t time.Time) (time.Duration, bool) {
+	if len(tr.events) == 0 {
+		return t.Sub(tr.Start), false
+	}
+	prev := tr.events[len(tr.events)-1].When
+	return t.Sub(prev), prev.Day() != t.Day()
+}
+
+func (tr *trace) addEvent(x interface{}, recyclable, sensitive bool) {
+	if DebugUseAfterFinish && tr.finishStack != nil {
+		buf := make([]byte, 4<<10) // 4 KB should be enough
+		n := runtime.Stack(buf, false)
+		log.Printf("net/trace: trace used after finish:\nFinished at:\n%s\nUsed at:\n%s", tr.finishStack, buf[:n])
+	}
+
+	/*
+		NOTE TO DEBUGGERS
+
+		If you are here because your program panicked in this code,
+		it is almost definitely the fault of code using this package,
+		and very unlikely to be the fault of this code.
+
+		The most likely scenario is that some code elsewhere is using
+		a trace.Trace after its Finish method is called.
+		You can temporarily set the DebugUseAfterFinish var
+		to help discover where that is; do not leave that var set,
+		since it makes this package much less efficient.
+	*/
+
+	e := event{When: time.Now(), What: x, Recyclable: recyclable, Sensitive: sensitive}
+	tr.mu.Lock()
+	e.Elapsed, e.NewDay = tr.delta(e.When)
+	if len(tr.events) < tr.maxEvents {
+		tr.events = append(tr.events, e)
+	} else {
+		// Discard the middle events.
+		di := int((tr.maxEvents - 1) / 2)
+		if d, ok := tr.events[di].What.(*discarded); ok {
+			(*d)++
+		} else {
+			// disc starts at two to count for the event it is replacing,
+			// plus the next one that we are about to drop.
+			tr.disc = 2
+			if tr.recycler != nil && tr.events[di].Recyclable {
+				go tr.recycler(tr.events[di].What)
+			}
+			tr.events[di].What = &tr.disc
+		}
+		// The timestamp of the discarded meta-event should be
+		// the time of the last event it is representing.
+		tr.events[di].When = tr.events[di+1].When
+
+		if tr.recycler != nil && tr.events[di+1].Recyclable {
+			go tr.recycler(tr.events[di+1].What)
+		}
+		copy(tr.events[di+1:], tr.events[di+2:])
+		tr.events[tr.maxEvents-1] = e
+	}
+	tr.mu.Unlock()
+}
+
+func (tr *trace) LazyLog(x fmt.Stringer, sensitive bool) {
+	tr.addEvent(x, true, sensitive)
+}
+
+func (tr *trace) LazyPrintf(format string, a ...interface{}) {
+	tr.addEvent(&lazySprintf{format, a}, false, false)
+}
+
+func (tr *trace) SetError() {
+	tr.mu.Lock()
+	tr.IsError = true
+	tr.mu.Unlock()
+}
+
+func (tr *trace) SetRecycler(f func(interface{})) {
+	tr.mu.Lock()
+	tr.recycler = f
+	tr.mu.Unlock()
+}
+
+func (tr *trace) SetTraceInfo(traceID, spanID uint64) {
+	tr.mu.Lock()
+	tr.traceID, tr.spanID = traceID, spanID
+	tr.mu.Unlock()
+}
+
+func (tr *trace) SetMaxEvents(m int) {
+	tr.mu.Lock()
+	// Always keep at least three events: first, discarded count, last.
+	if len(tr.events) == 0 && m > 3 {
+		tr.maxEvents = m
+	}
+	tr.mu.Unlock()
+}
+
+func (tr *trace) ref() {
+	atomic.AddInt32(&tr.refs, 1)
+}
+
+func (tr *trace) unref() {
+	if atomic.AddInt32(&tr.refs, -1) == 0 {
+		tr.mu.RLock()
+		if tr.recycler != nil {
+			// freeTrace clears tr, so we hold tr.recycler and tr.events here.
+			go func(f func(interface{}), es []event) {
+				for _, e := range es {
+					if e.Recyclable {
+						f(e.What)
+					}
+				}
+			}(tr.recycler, tr.events)
+		}
+		tr.mu.RUnlock()
+
+		freeTrace(tr)
+	}
+}
+
+func (tr *trace) When() string {
+	return tr.Start.Format("2006/01/02 15:04:05.000000")
+}
+
+func (tr *trace) ElapsedTime() string {
+	tr.mu.RLock()
+	t := tr.Elapsed
+	tr.mu.RUnlock()
+
+	if t == 0 {
+		// Active trace.
+		t = time.Since(tr.Start)
+	}
+	return fmt.Sprintf("%.6f", t.Seconds())
+}
+
+func (tr *trace) Events() []event {
+	tr.mu.RLock()
+	defer tr.mu.RUnlock()
+	return tr.events
+}
+
+var traceFreeList = make(chan *trace, 1000) // TODO(dsymonds): Use sync.Pool?
+
+// newTrace returns a trace ready to use.
+func newTrace() *trace {
+	select {
+	case tr := <-traceFreeList:
+		return tr
+	default:
+		return new(trace)
+	}
+}
+
+// freeTrace adds tr to traceFreeList if there's room.
+// This is non-blocking.
+func freeTrace(tr *trace) {
+	if DebugUseAfterFinish {
+		return // never reuse
+	}
+	tr.reset()
+	select {
+	case traceFreeList <- tr:
+	default:
+	}
+}
+
+func elapsed(d time.Duration) string {
+	b := []byte(fmt.Sprintf("%.6f", d.Seconds()))
+
+	// For subsecond durations, blank all zeros before decimal point,
+	// and all zeros between the decimal point and the first non-zero digit.
+	if d < time.Second {
+		dot := bytes.IndexByte(b, '.')
+		for i := 0; i < dot; i++ {
+			b[i] = ' '
+		}
+		for i := dot + 1; i < len(b); i++ {
+			if b[i] == '0' {
+				b[i] = ' '
+			} else {
+				break
+			}
+		}
+	}
+
+	return string(b)
+}
+
+var pageTmplCache *template.Template
+var pageTmplOnce sync.Once
+
+func pageTmpl() *template.Template {
+	pageTmplOnce.Do(func() {
+		pageTmplCache = template.Must(template.New("Page").Funcs(template.FuncMap{
+			"elapsed": elapsed,
+			"add":     func(a, b int) int { return a + b },
+		}).Parse(pageHTML))
+	})
+	return pageTmplCache
+}
+
+const pageHTML = `
+{{template "Prolog" .}}
+{{template "StatusTable" .}}
+{{template "Epilog" .}}
+
+{{define "Prolog"}}
+<html>
+	<head>
+	<title>/debug/requests</title>
+	<style type="text/css">
+		body {
+			font-family: sans-serif;
+		}
+		table#tr-status td.family {
+			padding-right: 2em;
+		}
+		table#tr-status td.active {
+			padding-right: 1em;
+		}
+		table#tr-status td.latency-first {
+			padding-left: 1em;
+		}
+		table#tr-status td.empty {
+			color: #aaa;
+		}
+		table#reqs {
+			margin-top: 1em;
+		}
+		table#reqs tr.first {
+			{{if $.Expanded}}font-weight: bold;{{end}}
+		}
+		table#reqs td {
+			font-family: monospace;
+		}
+		table#reqs td.when {
+			text-align: right;
+			white-space: nowrap;
+		}
+		table#reqs td.elapsed {
+			padding: 0 0.5em;
+			text-align: right;
+			white-space: pre;
+			width: 10em;
+		}
+		address {
+			font-size: smaller;
+			margin-top: 5em;
+		}
+	</style>
+	</head>
+	<body>
+
+<h1>/debug/requests</h1>
+{{end}} {{/* end of Prolog */}}
+
+{{define "StatusTable"}}
+<table id="tr-status">
+	{{range $fam := .Families}}
+	<tr>
+		<td class="family">{{$fam}}</td>
+
+		{{$n := index $.ActiveTraceCount $fam}}
+		<td class="active {{if not $n}}empty{{end}}">
+			{{if $n}}<a href="?fam={{$fam}}&b=-1{{if $.Expanded}}&exp=1{{end}}">{{end}}
+			[{{$n}} active]
+			{{if $n}}</a>{{end}}
+		</td>
+
+		{{$f := index $.CompletedTraces $fam}}
+		{{range $i, $b := $f.Buckets}}
+		{{$empty := $b.Empty}}
+		<td {{if $empty}}class="empty"{{end}}>
+		{{if not $empty}}<a href="?fam={{$fam}}&b={{$i}}{{if $.Expanded}}&exp=1{{end}}">{{end}}
+		[{{.Cond}}]
+		{{if not $empty}}</a>{{end}}
+		</td>
+		{{end}}
+
+		{{$nb := len $f.Buckets}}
+		<td class="latency-first">
+		<a href="?fam={{$fam}}&b={{$nb}}">[minute]</a>
+		</td>
+		<td>
+		<a href="?fam={{$fam}}&b={{add $nb 1}}">[hour]</a>
+		</td>
+		<td>
+		<a href="?fam={{$fam}}&b={{add $nb 2}}">[total]</a>
+		</td>
+
+	</tr>
+	{{end}}
+</table>
+{{end}} {{/* end of StatusTable */}}
+
+{{define "Epilog"}}
+{{if $.Traces}}
+<hr />
+<h3>Family: {{$.Family}}</h3>
+
+{{if or $.Expanded $.Traced}}
+  <a href="?fam={{$.Family}}&b={{$.Bucket}}">[Normal/Summary]</a>
+{{else}}
+  [Normal/Summary]
+{{end}}
+
+{{if or (not $.Expanded) $.Traced}}
+  <a href="?fam={{$.Family}}&b={{$.Bucket}}&exp=1">[Normal/Expanded]</a>
+{{else}}
+  [Normal/Expanded]
+{{end}}
+
+{{if not $.Active}}
+	{{if or $.Expanded (not $.Traced)}}
+	<a href="?fam={{$.Family}}&b={{$.Bucket}}&rtraced=1">[Traced/Summary]</a>
+	{{else}}
+	[Traced/Summary]
+	{{end}}
+	{{if or (not $.Expanded) (not $.Traced)}}
+	<a href="?fam={{$.Family}}&b={{$.Bucket}}&exp=1&rtraced=1">[Traced/Expanded]</a>
+        {{else}}
+	[Traced/Expanded]
+	{{end}}
+{{end}}
+
+{{if $.Total}}
+<p><em>Showing <b>{{len $.Traces}}</b> of <b>{{$.Total}}</b> traces.</em></p>
+{{end}}
+
+<table id="reqs">
+	<caption>
+		{{if $.Active}}Active{{else}}Completed{{end}} Requests
+	</caption>
+	<tr><th>When</th><th>Elapsed&nbsp;(s)</th></tr>
+	{{range $tr := $.Traces}}
+	<tr class="first">
+		<td class="when">{{$tr.When}}</td>
+		<td class="elapsed">{{$tr.ElapsedTime}}</td>
+		<td>{{$tr.Title}}</td>
+		{{/* TODO: include traceID/spanID */}}
+	</tr>
+	{{if $.Expanded}}
+	{{range $tr.Events}}
+	<tr>
+		<td class="when">{{.WhenString}}</td>
+		<td class="elapsed">{{elapsed .Elapsed}}</td>
+		<td>{{if or $.ShowSensitive (not .Sensitive)}}... {{.What}}{{else}}<em>[redacted]</em>{{end}}</td>
+	</tr>
+	{{end}}
+	{{end}}
+	{{end}}
+</table>
+{{end}} {{/* if $.Traces */}}
+
+{{if $.Histogram}}
+<h4>Latency (&micro;s) of {{$.Family}} over {{$.HistogramWindow}}</h4>
+{{$.Histogram}}
+{{end}} {{/* if $.Histogram */}}
+
+	</body>
+</html>
+{{end}} {{/* end of Epilog */}}
+`