// Create a new decoder that reads from an io.Reader.
d := sflow.NewDecoder(r)

// Attempt to decode an sFlow datagram.
dgram, err := d.Decode()
if err != nil {
	log.Println(err)
	return
}

for _, sample := range dgram.Samples {
	// Sample is an interface type
	if sample.SampleType() == sflow.TypeCounterSample {
		counterSample := sample.(sflow.CounterSample)

		for _, record := range counterSample.Records {
			// While there is a record.RecordType() method,
			// you can always check types directly.
			switch record.(type) {
			case sflow.HostDiskCounters:
				fmt.Printf("Max used percent of disk space is %d.\n",
					record.MaxUsedPercent)
			}
		}
	}
}