time: in NewTicker, document that the 1st tick comes after d

Fixes #42245

Change-Id: I3b298ab6be65569389873d68bd3c6e49cf892c69
Reviewed-on: https://go-review.googlesource.com/c/go/+/265818
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Rob Pike <[email protected]>
Trust: Alberto Donizetti <[email protected]>

src/time/tick.go

@@ -13,11 +13,12 @@ type Ticker struct {
  r runtimeTimer
 }
 
-// NewTicker returns a new Ticker containing a channel that will send the
-// time with a period specified by the duration argument.
-// It adjusts the intervals or drops ticks to make up for slow receivers.
-// The duration d must be greater than zero; if not, NewTicker will panic.
-// Stop the ticker to release associated resources.
+// NewTicker returns a new Ticker containing a channel that will send
+// the time on the channel after each tick. The period of the ticks is
+// specified by the duration argument. The ticker will adjust the time
+// interval or drop ticks to make up for slow receivers.
+// The duration d must be greater than zero; if not, NewTicker will
+// panic. Stop the ticker to release associated resources.
 func NewTicker(d Duration) *Ticker {
  if d <= 0 {
  panic(errors.New("non-positive interval for NewTicker"))