The handler function has this signature.

Sample handler:
```go
    handler :=  func(ctx context.Context, payload []byte, in <-chan []byte, out chan<- []byte) *RemoteErr {
        fmt.Println("Got request with initial payload", p, "from", GetCaller(ctx context.Context))
        fmt.Println("Subroute:", GetSubroute(ctx))
        for {
            select {

	getProgressFunc func() (int64, int64)
	bytesReturned   int64

	payloadBuffer      []byte
	payloadBufferIndex int
	payloadCh          chan *bytes.Buffer

	finBytesScanned, finBytesProcessed int64

	errCh  chan []byte
	doneCh chan struct{}
}

func (writer *messageWriter) write(data []byte) bool {
	if _, err := writer.writer.Write(data); err != nil {
		return false
	}

	// Use buffered channel to take care of burst sends or slow w.Write()
	mergeCh := make(chan []byte, globalAPIConfig.getRequestsPoolCapacity()*len(globalEndpoints.Hostnames()))
	localCh := make(chan event.Event, globalAPIConfig.getRequestsPoolCapacity())

	// Convert local messages to JSON and send to mergeCh
	go func() {

	globalIsTLS bool

	globalTLSCerts *certs.Manager

	globalHTTPServer        *xhttp.Server
	globalTCPOptions        xhttp.TCPOptions
	globalHTTPServerErrorCh = make(chan error)
	globalOSSignalCh        = make(chan os.Signal, 1)

	// global Trace system to send HTTP request/response
	// and Storage/OS calls info to registered listeners.
	globalTrace = pubsub.New[madmin.TraceInfo, madmin.TraceType](8)

func readMultipleFiles(ctx context.Context, disks []StorageAPI, req ReadMultipleReq, readQuorum int) ([]ReadMultipleResp, error) {
	resps := make([]chan ReadMultipleResp, len(disks))
	for i := range resps {
		resps[i] = make(chan ReadMultipleResp, len(req.Files))
	}
	g := errgroup.WithNErrs(len(disks))
	// Read files in parallel across disks.
	for index := range disks {
		index := index

	globalBucketObjectLockSys = &BucketObjectLockSys{}
	globalBucketVersioningSys = &BucketVersioningSys{}
	es := newExpiryState(context.Background(), objAPI, 0)
	workers := []chan expiryOp{make(chan expiryOp)}
	es.workers.Store(&workers)
	globalExpiryState = es
	var wg sync.WaitGroup
	wg.Add(1)
	expired := make([]ObjectToDelete, 0, 5)
	go func() {
		defer wg.Done()

	desc *prometheus.Desc
}

// Describe sends the super-set of all possible descriptors of metrics
func (c *minioCollector) Describe(ch chan<- *prometheus.Desc) {
	ch <- c.desc
}

// Collect is called by the Prometheus registry when collecting metrics.
func (c *minioCollector) Collect(ch chan<- prometheus.Metric) {
	// Expose MinIO's version information
	minioVersionInfo.WithLabelValues(Version, CommitID).Set(1.0)

	setIndex, poolIndex int
	queued              time.Time
	scanMode            madmin.HealScanMode
}

// mrfState sncapsulates all the information
// related to the global background MRF.
type mrfState struct {
	opCh chan partialOperation
}

// Add a partial S3 operation (put/delete) when one or more disks are offline.
func (m *mrfState) addPartialOp(op partialOperation) {
	if m == nil {
		return
	}

	select {

	case formatLZ4:
		r = lz4.NewReader(bf)
	case formatUnknown:
		r = bf
	default:
		return fmt.Errorf("Unsupported format %s", f)
	}
	tarReader := tar.NewReader(r)
	n := 0
	asyncWriters := make(chan struct{}, 16)
	var wg sync.WaitGroup

	var asyncErr error
	var asyncErrMu sync.Mutex
	for {
		if !o.ignoreErrs {
			asyncErrMu.Lock()
			err := asyncErr
			asyncErrMu.Unlock()
			if err != nil {

				}
			}(resultIndex, erObj)
		}
	}
	updateCloser := make(chan chan struct{})
	go func() {
		updateTicker := time.NewTicker(30 * time.Second)
		defer updateTicker.Stop()
		var lastUpdate time.Time

		// We need to merge since we will get the same buckets from each pool.
		// Therefore to get the exact bucket sizes we must merge before we can convert.
		var allMerged dataUsageCache

		update := func() {