Some code improvements

* Some assignments simplified by using assignment operators
* Rewrite switch statement with only one case as if.
* Rewrite if-else chain as a switch statement.
* go fmt `modules/todoist/project.go` file.

modules/textfile/widget.go

@@ -76,9 +76,9 @@ func (widget *Widget) display() {
 	text := widget.settings.common.SigilStr(len(widget.Sources), widget.Idx, width) + "\n"
 
 	if widget.settings.format {
-		text = text + widget.formattedText()
+		text += widget.formattedText()
 	} else {
-		text = text + widget.plainText()
+		text += widget.plainText()
 	}
 
 	widget.Redraw(title, text, true)