protected final void maybeCancel() {
        if (!closeCalled) {
            cancelled = true;
            try (SafeCloseable ignore = ctx.push()) {
                close(new ServerStatusAndMetadata(Status.CANCELLED, new Metadata(), true));
            }
        }
    }
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