add ping try & fix least

pool.go

@@ -54,7 +54,7 @@ func New(ctx context.Context) *Pool {
 		TryOnSleep:      time.Second,
 		Balance:         BalanceLeastConn,
 		PingTimout:      time.Second * 5,
-		PingTry: 5,
+		PingTry:         5,
 	}
 }
 
@@ -84,7 +84,7 @@ func (d *Pool) WithContext(ctx context.Context) *Pool {
 		TryOnSleep:      d.TryOnSleep,
 		Balance:         d.Balance,
 		PingTimout:      d.PingTimout,
-		PingTry: d.PingTry,
+		PingTry:         d.PingTry,
 	}
 }