tests: make test more tolerant to windows low precision timer default interval

vlib/sync/channel_select_3_test.v

@@ -21,7 +21,9 @@ fn f1(ch1 chan int, ch2 chan St, ch3 chan int, ch4 chan int, ch5 chan int, sem s
 		ch3 <- 5 {
 			a = 1
 		}
-		ch2 <- St{a: 37} {
+		ch2 <- St{
+			a: 37
+		} {
 			a = 2
 		}
 		ch4 <- (6 + 7 * 9) {
@@ -56,7 +58,7 @@ fn f2(ch1 chan St, ch2 chan int, sem sync.Semaphore) {
 		}
 	}
 	sem.post()
-} 
+}
 
 fn test_select_blocks() {
 	ch1 := chan int{cap: 1}
@@ -67,7 +69,7 @@ fn test_select_blocks() {
 	sem := sync.new_semaphore()
 	mut r := false
 	t := select {
-		b := <- ch1 {
+		b := <-ch1 {
 			println(b)
 		}
 		else {
@@ -80,20 +82,26 @@ fn test_select_blocks() {
 	go f2(ch2, ch3, sem)
 	n := <-ch3
 	assert n == 23
-	ch2 <- St{a: 13}
+	ch2 <- St{
+		a: 13
+	}
 	sem.wait()
 	stopwatch := time.new_stopwatch({})
 	go f1(ch1, ch2, ch3, ch4, ch5, sem)
 	sem.wait()
 	elapsed_ms := f64(stopwatch.elapsed()) / time.millisecond
-	assert elapsed_ms >= 295.0
+	// https://docs.microsoft.com/en-us/windows-hardware/drivers/kernel/high-resolution-timers
+	// > For example, for Windows running on an x86 processor, the default interval between 
+	// > system clock ticks is typically about 15 milliseconds, and the minimum interval 
+	// > between system clock ticks is about 1 millisecond.
+	assert elapsed_ms >= 280.0 // 300 - (15ms + 5ms just in case)
 
 	ch1.close()
 	ch2.close()
 	mut h := 7
 	mut is_open := true
 	if select {
-		b := <- ch2 {
+		_ := <-ch2 {
 			h = 0
 		}
 		ch1 <- h {
@@ -112,5 +120,3 @@ fn test_select_blocks() {
 	// since all channels are closed `select` should return `false`
 	assert is_open == false
 }
-
-