net/http: use t.Deadline instead of an arbitrary timeout in TestServerConnState

Updates #37322

Change-Id: I3b8369cd9e0ed5e4b3136cedaa2f70698ead2270
Reviewed-on: https://go-review.googlesource.com/c/go/+/222957
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>

src/net/http/serve_test.go

@@ -4135,10 +4135,19 @@ func TestServerConnState(t *testing.T) {
 
 		doRequests()
 
-		timer := time.NewTimer(5 * time.Second)
+		stateDelay := 5 * time.Second
+		if deadline, ok := t.Deadline(); ok {
+			// Allow an arbitrarily long delay.
+			// This test was observed to be flaky on the darwin-arm64-corellium builder,
+			// so we're increasing the deadline to see if it starts passing.
+			// See https://golang.org/issue/37322.
+			const arbitraryCleanupMargin = 1 * time.Second
+			stateDelay = time.Until(deadline) - arbitraryCleanupMargin
+		}
+		timer := time.NewTimer(stateDelay)
 		select {
 		case <-timer.C:
-			t.Errorf("Timed out waiting for connection to change state.")
+			t.Errorf("Timed out after %v waiting for connection to change state.", stateDelay)
 		case <-complete:
 			timer.Stop()
 		}