Extend linter rules (#1300)

- dupword checks for duplicate words in the source code
- durationcheck checks for two durations multiplied together
- forbidigo forbids identifiers
- mirror reports wrong mirror patterns of bytes/strings usage
- misspell finds commonly misspelled English words in comments
- predeclared finds code that shadows one of Go's predeclared identifiers
- thelper detects Go test helpers without t.Helper() call and checks the consistency of test helpers

client/ui/client_ui.go

@@ -69,7 +69,7 @@ func main() {
 		a.Run()
 	} else {
 		if err := checkPIDFile(); err != nil {
-			fmt.Println(err)
+			log.Errorf("check PID file: %v", err)
 			return
 		}
 		systray.Run(client.onTrayReady, client.onTrayExit)