pkg\sky_engine\lib\_http\websocket.dart
/// A ping message is sent every [pingInterval], starting at the first
/// [pingInterval] after a new value has been assigned or a pong message has
/// been received. If a ping message is not answered by a pong message from the
/// peer, the `WebSocket` is assumed disconnected and the connection is closed
/// with a [WebSocketStatus.goingAway] close code. When a ping signal is sent,
/// the pong message must be received within [pingInterval].