TUN-1562: Refactor connectedSignal to be safe to close multiple times

signal/safe_signal_test.go

@@ -0,0 +1,25 @@
+package signal
+
+import (
+	"testing"
+)
+
+func TestMultiNotifyDoesntCrash(t *testing.T) {
+	sig := New(make(chan struct{}))
+	sig.Notify()
+	sig.Notify()
+	// If code has reached here without crashing, the test has passed.
+}
+
+func TestWait(t *testing.T) {
+	sig := New(make(chan struct{}))
+	sig.Notify()
+	select {
+	case <-sig.Wait():
+		// Test succeeds
+		return
+	default:
+		// sig.Wait() should have been read from, because sig.Notify() wrote to it.
+		t.Fail()
+	}
+}