[#7] loki: Fix linter issues

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

logging/lokicore/loki/example/main.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"fmt"
+	"os"
 	"strconv"
 	"sync"
 	"time"
@@ -19,7 +21,10 @@ func send(loki *loki.Client) {
 
 	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())
+			err := loki.Send(strconv.Itoa(j)+" "+strconv.Itoa(i)+" test log message", time.Now())
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "send: %v", err)
+			}
 		}
 		time.Sleep(20 * time.Millisecond)
 	}

logging/lokicore/loki/log.go

@@ -6,8 +6,9 @@ import (
 	"time"
 )
 
+// Send sends the message to the loki server.
 // If the client is disabled, it returns error.
-// If the entries channel is full, the message is discarded and returns error
+// If the entries channel is full, the message is discarded and returns error.
 func (client *Client) Send(msg string, timestamp time.Time) error {
 	if !client.IsEnabled() {
 		client.missedMessages++