private void invokeOnCancel() {
        try (SafeCloseable ignored = ctx.push()) {
            if (listener != null) {
                listener.onCancel();
            }
        } catch (Throwable t) {
            if (!closeCalled) {
                // A custom error when dealing with client cancel or transport issues should be
                // returned. We have already closed the listener, so it will not receive any more
                // callbacks as designed.
                close(t);
            }
        }
    }
Cancels a call when the call was closed by a client, not by server.
grpc/src/main/java/com/linecorp/armeria/internal/server/grpc/AbstractServerCall.java