Replace standard log package with logrus

The standard "log" package was replaced by the structured logger "github.com/sirupsen/logrus" for better log control in various files. This change will allow to tailor the logging information more precisely and make logs easier to read and analyze. All calls of standard log methods were replaced by their logrus counterparts.

cmd/root.go

@@ -2,7 +2,6 @@ package cmd
 
 import (
 	"fmt"
-	"log"
 	"os"
 	"os/signal"
 	"path"
@@ -11,6 +10,8 @@ import (
 	"syscall"
 	"time"
 
+	log "github.com/sirupsen/logrus"
+
 	"github.com/fsnotify/fsnotify"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"