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.

wtf/billboard_modal.go

@@ -11,8 +11,7 @@ const modalHeight = 22
 
 func NewBillboardModal(text string, closeFunc func()) *tview.Frame {
 	keyboardIntercept := func(event *tcell.EventKey) *tcell.EventKey {
-		switch string(event.Rune()) {
-		case "/":
+		if string(event.Rune()) == "/" {
 			closeFunc()
 			return nil
 		}

wtf/focus_tracker.go

@@ -152,7 +152,7 @@ func (tracker *FocusTracker) blur(idx int) {
 }
 
 func (tracker *FocusTracker) decrement() {
-	tracker.Idx = tracker.Idx - 1
+	tracker.Idx--
 
 	if tracker.Idx < 0 {
 		tracker.Idx = len(tracker.focusables()) - 1
@@ -216,7 +216,7 @@ func (tracker *FocusTracker) focusState() FocusState {
 }
 
 func (tracker *FocusTracker) increment() {
-	tracker.Idx = tracker.Idx + 1
+	tracker.Idx++
 
 	if tracker.Idx == len(tracker.focusables()) {
 		tracker.Idx = 0

wtf/keyboard_widget.go

@@ -89,12 +89,12 @@ func (widget *KeyboardWidget) HelpText() string {
 	str := "Keyboard commands for " + widget.settings.Module.Type + "\n\n"
 
 	for _, item := range widget.charHelp {
-		str = str + fmt.Sprintf("  [%s]: %s\n", item.Key, item.Text)
+		str += fmt.Sprintf("  [%s]: %s\n", item.Key, item.Text)
 	}
-	str = str + "\n\n"
+	str += "\n\n"
 
 	for _, item := range widget.keyHelp {
-		str = str + fmt.Sprintf("  [%-*s]: %s\n", widget.maxKey, item.Key, item.Text)
+		str += fmt.Sprintf("  [%-*s]: %s\n", widget.maxKey, item.Key, item.Text)
 	}
 
 	return str

wtf/multisource_widget.go

@@ -45,7 +45,7 @@ func (widget *MultiSourceWidget) CurrentSource() string {
 // Next displays the next source in the source list. If the current source is the last
 // source it wraps around to the first source
 func (widget *MultiSourceWidget) NextSource() {
-	widget.Idx = widget.Idx + 1
+	widget.Idx++
 	if widget.Idx == len(widget.Sources) {
 		widget.Idx = 0
 	}
@@ -58,7 +58,7 @@ func (widget *MultiSourceWidget) NextSource() {
 // Prev displays the previous source in the source list. If the current source is the first
 // source, it wraps around to the last source
 func (widget *MultiSourceWidget) PrevSource() {
-	widget.Idx = widget.Idx - 1
+	widget.Idx--
 	if widget.Idx < 0 {
 		widget.Idx = len(widget.Sources) - 1
 	}