Use monotonic time for the timer driver

Use the arbitrary monotonic timer which supports higher resolution.
This avoids Epochalypse problems (even if we are going to be mostly
dead by 2038).

.gitignore

@@ -1,2 +1,3 @@
 tests/test_box_and_client
 tests/test_dsl
+tests/test_timer

src/syndicate/drivers/timers.nim

@@ -1,25 +1,25 @@
 # SPDX-License-Identifier: ISC
 
-import std/[asyncdispatch, times]
+import std/[asyncdispatch, monotimes, times]
 import preserves, preserves/records
 import syndicate
 
 const TimeLaterThan* = RecordClass(label: symbol"TimeLaterThan", arity: 1)
 
-proc toPreserveHook*(time: Time): Preserve =
-  %time.toUnixFloat
+proc toPreserveHook*(time: Monotime): Preserve =
+  %time.ticks
 
-proc fromPreserveHook*(result: var Time; p: Preserve) =
-  if p.kind != pkDouble:
+proc fromPreserveHook*(result: var Monotime; p: Preserve) =
+  if p.kind != pkSignedInteger:
     raise newException(ValueError, "not a preserved time: " & $p)
-  result = fromUnixFloat(p.double)
+  result = cast[MonoTime]((p.int.int64,))
 
 syndicate timerDriver:
 
   spawn "timer":
-    during(Observe % (TimeLaterThan % `?*`)) do (deadline: Time):
+    during(Observe % (TimeLaterThan % `?*`)) do (deadline: MonoTime):
       let
-        now = getTime()
+        now = getMonoTime()
         period = inMilliseconds(deadline - now)
       if period > 0:
         getCurrentFacet().beginExternalTask()

tests/test_timer.nim

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: ISC
 
-import std/[asyncdispatch, times]
+import std/[asyncdispatch, monotimes, times]
 import preserves, preserves/records
 import syndicate
 
@@ -10,14 +10,14 @@ syndicate plainTimerDemo:
   boot timerDriver
 
   spawn "laterThanDemo":
-    field(deadline, Time, getTime())
+    field(deadline, MonoTime, getMonoTime())
     field(count, int, 0)
 
     onAsserted(TimeLaterThan % deadline.get) do ():
       echo "TimeLaterThan ticked for deadline ", deadline.get
       count.set(count.get.succ)
       if count.get < 5:
-        deadline.set(deadline.get + 500.milliseconds)
+        deadline.set(getMonoTime() + initDuration(milliseconds = 500))
 
     onStop:
       echo "dataspace stopped"