all: drop support for Go 1.16 and Go 1.17

src/runtime/timer.go

@@ -0,0 +1,33 @@
+// Portions copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+type puintptr uintptr
+
+// Package time knows the layout of this structure.
+// If this struct changes, adjust ../time/sleep.go:/runtimeTimer.
+type timer struct {
+	// If this timer is on a heap, which P's heap it is on.
+	// puintptr rather than *p to match uintptr in the versions
+	// of this struct defined in other packages.
+	pp puintptr
+
+	// Timer wakes up at when, and then at when+period, ... (period > 0 only)
+	// each time calling f(arg, now) in the timer goroutine, so f must be
+	// a well-behaved function and not block.
+	//
+	// when must be positive on an active timer.
+	when   int64
+	period int64
+	f      func(any, uintptr)
+	arg    any
+	seq    uintptr
+
+	// What to set the when field to in timerModifiedXX status.
+	nextwhen int64
+
+	// The status field holds one of the values below.
+	status uint32
+}