go/src/runtime/time_nofake.go

var faketime …

// Exported via linkname for use by time and internal/poll.
//
// Many external packages also linkname nanotime for a fast monotonic time.
// Such code should be updated to use:
//
//	var start = time.Now() // at init time
//
// and then replace nanotime() with time.Since(start), which is equally fast.
//
// However, all the code linknaming nanotime is never going to go away.
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname nanotime
//go:nosplit
func nanotime() int64 { … }

var overrideWrite …

// write must be nosplit on Windows (see write1)
//
//go:nosplit
func write(fd uintptr, p unsafe.Pointer, n int32) int32 { … }