vlib/context: some clean up and more readable examples (#9868)

vlib/context/deadline_test.v

@@ -6,15 +6,6 @@ const (
 	short_duration = 1 * time.millisecond
 )
 
-fn after(dur time.Duration) chan int {
-	dst := chan int{}
-	go fn (dur time.Duration, dst chan int) {
-		time.sleep(dur)
-		dst <- 0
-	}(dur, dst)
-	return dst
-}
-
 // This example passes a context with an arbitrary deadline to tell a blocking
 // function that it should abandon its work as soon as it gets to it.
 fn test_with_deadline() {
@@ -28,14 +19,11 @@ fn test_with_deadline() {
 		context.cancel(ctx)
 	}
 
-	after_ch := after(1 * time.second)
 	ctx_ch := ctx.done()
 	select {
-		_ := <-after_ch {
-			assert false
-		}
-		_ := <-ctx_ch {
-			assert true
+		_ := <-ctx_ch {}
+		> 1 * time.second {
+			panic('This should not happen')
 		}
 	}
 }
@@ -50,14 +38,11 @@ fn test_with_timeout() {
 		context.cancel(ctx)
 	}
 
-	after_ch := after(1 * time.second)
 	ctx_ch := ctx.done()
 	select {
-		_ := <-after_ch {
-			assert false
-		}
-		_ := <-ctx_ch {
-			assert true
+		_ := <-ctx_ch {}
+		> 1 * time.second {
+			panic('This should not happen')
 		}
 	}
 }