err = Errorf(
				"region '%s' is invalid, expected simple characters such as [us-east-1, myregion...]",
				region)
			return
		}
		s.region = region
	}

	name := env.Get(EnvSiteName, siteKV.Get(NameKey))
	if name != "" {
		if !validSiteNameRegex.MatchString(name) {
			err = Errorf(
				"site name '%s' is invalid, expected simple characters such as [cal-rack0, myname...]",
				name)
			return

	scannerMetricLastRealtime

	// Trace only metrics:
	scannerMetricScanFolder      // Scan a folder on disk, recursively.
	scannerMetricScanCycle       // Full cycle, cluster global
	scannerMetricScanBucketDrive // Single bucket on one drive
	scannerMetricCompactFolder   // Folder compacted.

	// Must be last:
	scannerMetricLast
)

// log scanner action.
// Use for s > scannerMetricStartTrace

type queueItem struct {
	input []byte          // raw input sent to the worker
	dst   chan [][]string // result of block decode
	err   error           // any error encountered will be set here
}

// Read - reads single record.
// Once Read is called the previous record should no longer be referenced.
func (r *Reader) Read(dst sql.Record) (sql.Record, error) {
	// If we have have any records left, return these before any error.

	CurrentQueuedCalls int64 // Deprecated
	EventsErrorsTotal  int64 // Deprecated
	CurrentSendCalls   int64 // Deprecated

	TargetStats map[TargetID]TargetStat
}

// TargetStat is the stats of a single target.
type TargetStat struct {
	CurrentSendCalls int64 // CurrentSendCalls is the number of concurrent async Send calls to all targets
	CurrentQueue     int   // Populated if target has a store.
	TotalEvents      int64

		}
		if _, err := store.Put(item); err != nil {
			t.Fatalf("unable to store.Put(); %v", err)
		}
		items = append(items, item)
	}

	keys := store.List()
	if len(keys) != 6 {
		// 1 multiple + 5 single PUTs
		t.Fatalf("expected len(keys)=6, but found %d", len(keys))
	}

	var resultItems []TestItem
	for _, key := range keys {
		if key.ItemCount > 1 {
			items, err := store.GetMultiple(key)

  optional string name = 1;

  // singularName is the singular name of the resource.  This allows clients to handle plural and singular opaquely.
  // The singularName is more correct for reporting status on a single item and both singular and plural are allowed
  // from the kubectl CLI interface.
  optional string singularName = 6;

  // namespaced indicates if a resource is namespaced or not.
  optional bool namespaced = 2;

any 6.out that imports the first two files.

The stanza

	// #include <gmp.h>
	import "C"

is a signal to cgo.  The doc comment on the import of "C" provides
additional context for the C file.  Here it is just a single #include
but it could contain arbitrary C definitions to be imported and used.

Cgo recognizes any use of a qualified identifier C.xxx and uses gcc to
find the definition of xxx.  If xxx is a type, cgo replaces C.xxx with

	if !ok {
		return "", "", s, ErrHeader
	}

	if !validPAXRecord(k, v) {
		return "", "", s, ErrHeader
	}
	return k, v, rem, nil
}

// formatPAXRecord formats a single PAX record, prefixing it with the
// appropriate length.
func formatPAXRecord(k, v string) (string, error) {
	if !validPAXRecord(k, v) {
		return "", ErrHeader
	}

* Share database connections.
* Enforce security, authentication, role requirements, etc.
* And many other things...

All these, while minimizing code repetition.

## First Steps

Let's see a very simple example. It will be so simple that it is not very useful, for now.

But this way we can focus on how the **Dependency Injection** system works.

### Create a dependency, or "dependable"

Let's first focus on the dependency.

import okhttp3.Response
import okhttp3.internal.platform.Platform
import okhttp3.internal.publicsuffix.PublicSuffixDatabase

/**
 * [DNS over HTTPS implementation][doh_spec].
 *
 * > A DNS API client encodes a single DNS query into an HTTP request
 * > using either the HTTP GET or POST method and the other requirements
 * > of this section.  The DNS API server defines the URI used by the
 * > request through the use of a URI Template.
 *