Minor tweak

src/Discord.Net/Net/WebSockets/Commands.cs

@@ -14,9 +14,8 @@ namespace Discord.Net.WebSockets
 		public sealed class KeepAlive : WebSocketMessage<ulong>
 		{
 			public KeepAlive() : base(1, GetTimestamp()) { }
-			private static DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
-			private static ulong GetTimestamp()
-				=> (ulong)(DateTime.UtcNow - epoch).TotalMilliseconds;
+			private static readonly DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+			private static ulong GetTimestamp() => (ulong)(DateTime.UtcNow - epoch).TotalMilliseconds;
 		}
 		public sealed class Login : WebSocketMessage<Login.Data>
 		{