add helper function to determine logger level (#1321)

* add helper function to determine logger level

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

logger/level.go

@@ -115,3 +115,12 @@ func Fatalf(template string, args ...interface{}) {
 	DefaultLogger.Logf(FatalLevel, template, args...)
 	os.Exit(1)
 }
+
+// Returns true if the given level is at or above the current logger level
+func V(lvl Level, log Logger) bool {
+	l := DefaultLogger
+	if log != nil {
+		l = log
+	}
+	return l.Options().Level >= lvl
+}