Add log level color keys and handle default (#264)

* Add log level color keys

Also adding a default white color when the key is not recognize. Without
the default an error is printed instead of the log entry.

* Fallback to default terminal color on unknown log level

Co-authored-by: Takashi Kusumi <tkusumi@zlab.co.jp>

---------

Co-authored-by: Takashi Kusumi <tkusumi@zlab.co.jp>

cmd/cmd.go

@@ -486,6 +486,8 @@ func (o *options) generateTemplate() (*template.Template, error) {
 				levelColor = color.New(color.FgBlue)
 			case "warn":
 				levelColor = color.New(color.FgYellow)
+			case "warning":
+				levelColor = color.New(color.FgYellow)
 			case "error":
 				levelColor = color.New(color.FgRed)
 			case "dpanic":
@@ -494,7 +496,10 @@ func (o *options) generateTemplate() (*template.Template, error) {
 				levelColor = color.New(color.FgRed)
 			case "fatal":
 				levelColor = color.New(color.FgCyan)
+			case "critical":
+				levelColor = color.New(color.FgCyan)
 			default:
+				return level
 			}
 			return levelColor.SprintFunc()(level)
 		},