Allow specifying Url from env

docs/configuration.md

@@ -694,7 +694,7 @@ The title used to indicate the site.
 
 `url`
 
-The URL which will be requested and its response will determine the status of the site.
+The URL which will be requested and its response will determine the status of the site. Optionally, you can specify this using an environment variable with the syntax `${VARIABLE_NAME}`.
 
 `icon`
 

internal/widget/monitor.go

@@ -47,7 +47,7 @@ type Monitor struct {
 	widgetBase `yaml:",inline"`
 	Sites      []struct {
 		Title       string            `yaml:"title"`
-		Url         string           `yaml:"url"`
+		Url         OptionalEnvString `yaml:"url"`
 		IconUrl     string            `yaml:"icon"`
 		SameTab     bool              `yaml:"same-tab"`
 		Status      *feed.SiteStatus  `yaml:"-"`
@@ -66,7 +66,7 @@ func (widget *Monitor) Update(ctx context.Context) {
 	requests := make([]*http.Request, len(widget.Sites))
 
 	for i := range widget.Sites {
-		request, err := http.NewRequest("GET", widget.Sites[i].Url, nil)
+		request, err := http.NewRequest("GET", string(widget.Sites[i].Url), nil)
 
 		if err != nil {
 			message := fmt.Errorf("failed to create http request for %s: %s", widget.Sites[i].Url, err)