Add suport for DoH over HTTP/3

vendor/github.com/lucas-clemente/quic-go/internal/utils/timer.go

@@ -0,0 +1,53 @@
+package utils
+
+import (
+	"math"
+	"time"
+)
+
+// A Timer wrapper that behaves correctly when resetting
+type Timer struct {
+	t        *time.Timer
+	read     bool
+	deadline time.Time
+}
+
+// NewTimer creates a new timer that is not set
+func NewTimer() *Timer {
+	return &Timer{t: time.NewTimer(time.Duration(math.MaxInt64))}
+}
+
+// Chan returns the channel of the wrapped timer
+func (t *Timer) Chan() <-chan time.Time {
+	return t.t.C
+}
+
+// Reset the timer, no matter whether the value was read or not
+func (t *Timer) Reset(deadline time.Time) {
+	if deadline.Equal(t.deadline) && !t.read {
+		// No need to reset the timer
+		return
+	}
+
+	// We need to drain the timer if the value from its channel was not read yet.
+	// See https://groups.google.com/forum/#!topic/golang-dev/c9UUfASVPoU
+	if !t.t.Stop() && !t.read {
+		<-t.t.C
+	}
+	if !deadline.IsZero() {
+		t.t.Reset(time.Until(deadline))
+	}
+
+	t.read = false
+	t.deadline = deadline
+}
+
+// SetRead should be called after the value from the chan was read
+func (t *Timer) SetRead() {
+	t.read = true
+}
+
+// Stop stops the timer
+func (t *Timer) Stop() {
+	t.t.Stop()
+}