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| -rw-r--r-- | doc/next/6-stdlib/1-time.md | 30 |
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diff --git a/doc/next/6-stdlib/1-time.md b/doc/next/6-stdlib/1-time.md new file mode 100644 index 0000000000..fbd8fc740a --- /dev/null +++ b/doc/next/6-stdlib/1-time.md @@ -0,0 +1,30 @@ +### Timer changes + +Go 1.23 makes two significant changes to the implementation of +[`time.Timer`](/pkg/time#Timer) and [`time.Ticker`](/pkg/time#Ticker). + +First, `Timer`s and `Ticker`s that are no longer referred to by the program +become eligible for garbage collection immediately, even if their +`Stop` methods have not been called. +Earlier versions of Go did not collect unstopped `Timer`s until after +they had fired and never collected unstopped `Ticker`s. + +Second, the timer channel associated with a `Timer` or `Ticker` is +now unbuffered, with capacity 0. +The main effect of this change is that Go now guarantees +that for any call to a `Reset` or `Stop` method, no stale values +prepared before that call will be sent or received after the call. +Earlier versions of Go used channels with a one-element buffer, +making it difficult to use `Reset` and `Stop` correctly. +A visible effect of this change is that `len` and `cap` of timer channels +now returns 0 instead of 1, which may affect programs that +poll the length to decide whether a receive on the timer channel +will succeed. +Such code should use a non-blocking receive instead. + +These new behaviors are only enabled when the main Go program +is in a module with a `go.mod` `go` line using Go 1.23.0 or later. +When Go 1.23 builds older programs, the old behaviors remain in effect. +The new [GODEBUG setting](/doc/godebug) [`asynctimerchan=1`](/pkg/time/#NewTimer) +can be used to revert back to asynchronous channel behaviors +even when a program names Go 1.23.0 or later in its `go.mod` file. |