switch to new sync/atomic helpers in go1.19 (#728)

These new helpers make the code a lot cleaner. I confirmed that the
simple helpers like `atomic.Int64` don't add any extra overhead as they
get inlined by the compiler. `atomic.Pointer` adds an extra method call
as it no longer gets inlined, but we aren't using these on the hot path
so it is probably okay.

relay_manager.go

@@ -13,9 +13,9 @@ import (
 )
 
 type relayManager struct {
-	l             *logrus.Logger
-	hostmap       *HostMap
-	atomicAmRelay int32
+	l       *logrus.Logger
+	hostmap *HostMap
+	amRelay atomic.Bool
 }
 
 func NewRelayManager(ctx context.Context, l *logrus.Logger, hostmap *HostMap, c *config.C) *relayManager {
@@ -41,18 +41,11 @@ func (rm *relayManager) reload(c *config.C, initial bool) error {
 }
 
 func (rm *relayManager) GetAmRelay() bool {
-	return atomic.LoadInt32(&rm.atomicAmRelay) == 1
+	return rm.amRelay.Load()
 }
 
 func (rm *relayManager) setAmRelay(v bool) {
-	var val int32
-	switch v {
-	case true:
-		val = 1
-	case false:
-		val = 0
-	}
-	atomic.StoreInt32(&rm.atomicAmRelay, val)
+	rm.amRelay.Store(v)
 }
 
 // AddRelay finds an available relay index on the hostmap, and associates the relay info with it.