[#5] logs: Add Loki

Signed-off-by: Alexander Chuprov <a.chuprov@yadro.com>

logging/lokicore/loki/example/main.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"strconv"
+	"sync"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/logging/lokicore/loki"
+)
+
+var wg sync.WaitGroup
+
+const countMsgGroup = 100
+const countMsg = 500000
+
+func send(loki *loki.Client) {
+	wg.Add(1)
+	defer wg.Done()
+
+	for j := 0; j < countMsg/countMsgGroup; j++ {
+		for i := 0; i < countMsgGroup; i++ {
+			loki.Send(strconv.Itoa(j)+" "+strconv.Itoa(i)+" test log message", time.Now())
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+}
+
+func main() {
+	loki := loki.Setup(loki.Config{
+		Endpoint: "localhost:3100/api/prom/push",
+		Labels: map[string]string{
+			"label": "test",
+		},
+		BatchWait:          1000,
+		BatchEntriesNumber: 200,
+		Enabled:            true,
+	})
+	go send(loki)
+	send(loki)
+
+	wg.Wait()
+	loki.Shutdown()
+}