Go 1.23 makes two significant changes to the implementation of [time.Timer] and [time.Ticker].
First, Timers and Tickers 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 Timers until after they had fired and never collected unstopped Tickers.
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 asynctimerchan=1 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.