all: use time.Until where applicable

Updates #14595

Change-Id: Idf60b3004c7a0ebb59dd48389ab62c854069e09f
Reviewed-on: https://go-review.googlesource.com/28073
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/context/context.go

@@ -376,7 +376,7 @@ func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc) {
 		deadline:  deadline,
 	}
 	propagateCancel(parent, c)
-	d := deadline.Sub(time.Now())
+	d := time.Until(deadline)
 	if d <= 0 {
 		c.cancel(true, DeadlineExceeded) // deadline has already passed
 		return c, func() { c.cancel(true, Canceled) }
@@ -406,7 +406,7 @@ func (c *timerCtx) Deadline() (deadline time.Time, ok bool) {
 }
 
 func (c *timerCtx) String() string {
-	return fmt.Sprintf("%v.WithDeadline(%s [%s])", c.cancelCtx.Context, c.deadline, c.deadline.Sub(time.Now()))
+	return fmt.Sprintf("%v.WithDeadline(%s [%s])", c.cancelCtx.Context, c.deadline, time.Until(c.deadline))
 }
 
 func (c *timerCtx) cancel(removeFromParent bool, err error) {

src/crypto/tls/tls.go

@@ -102,7 +102,7 @@ func DialWithDialer(dialer *net.Dialer, network, addr string, config *Config) (*
 	timeout := dialer.Timeout
 
 	if !dialer.Deadline.IsZero() {
-		deadlineTimeout := dialer.Deadline.Sub(time.Now())
+		deadlineTimeout := time.Until(dialer.Deadline)
 		if timeout == 0 || deadlineTimeout < timeout {
 			timeout = deadlineTimeout
 		}

src/net/fd_poll_runtime.go

@@ -122,7 +122,7 @@ func (fd *netFD) setWriteDeadline(t time.Time) error {
 }
 
 func setDeadlineImpl(fd *netFD, t time.Time, mode int) error {
-	diff := int64(t.Sub(time.Now()))
+	diff := int64(time.Until(t))
 	d := runtimeNano() + diff
 	if d <= 0 && diff > 0 {
 		// If the user has a deadline in the future, but the delay calculation

src/net/http/client.go

@@ -324,7 +324,7 @@ func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTi
 	var once sync.Once
 	stopTimer = func() { once.Do(func() { close(stopTimerCh) }) }
 
-	timer := time.NewTimer(deadline.Sub(time.Now()))
+	timer := time.NewTimer(time.Until(deadline))
 	go func() {
 		select {
 		case <-initialReqCancel:

src/net/http/serve_test.go

@@ -1737,7 +1737,7 @@ restart:
 		if !c.rd.IsZero() {
 			// If the deadline falls in the middle of our sleep window, deduct
 			// part of the sleep, then return a timeout.
-			if remaining := c.rd.Sub(time.Now()); remaining < cue {
+			if remaining := time.Until(c.rd); remaining < cue {
 				c.script[0] = cue - remaining
 				time.Sleep(remaining)
 				return 0, syscall.ETIMEDOUT