private void close(ServerStatusAndMetadata statusAndMetadata, @Nullable Throwable exception) {
        if (ctx.eventLoop().inEventLoop()) {
            doClose(statusAndMetadata, exception);
        } else {
            ctx.eventLoop().execute(() -> {
                doClose(statusAndMetadata, exception);
            });
        }
    }
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