Fix: format flag not working (#410)

core/config.go

@@ -84,10 +84,19 @@ func LoadConfig(formatName string, input interface{}) (*Config, error) {
 		formats := make([]string, len(v))
 		hasProtobuf := false
 		for i, file := range v {
-			f := getFormat(file)
+			var f string
+
+			if formatName == "auto" {
+				f = getFormat(file)
+				if f == "" {
+					return nil, newError("Unable to get format of", formatName).AtWarning()
+				}
+			}
+
 			if f == "" {
 				f = formatName
 			}
+
 			if f == "protobuf" {
 				hasProtobuf = true
 			}