protected final ChannelFuture goAway(ChannelHandlerContext ctx, int lastStreamId) {
        return goAway(ctx, lastStreamId, NO_ERROR.code(), goAwayDebugData, ctx.newPromise());
    }
Sends a {@code GO_AWAY} frame to initiate connection shutdown. No-op if channel isn't active.
Does <strong>not</strong> flush immediately, this is the responsibility of the caller.
core/src/main/java/com/linecorp/armeria/internal/common/AbstractHttp2ConnectionHandler.java