implement functions to augment the context

pkg/thumbnail/imgsource/imgsource.go

@@ -5,7 +5,26 @@ import (
 	"image"
 )
 
+type key int
+
+const (
+	auth key = iota
+)
+
 // Source defines the interface for image sources
 type Source interface {
 	Get(ctx context.Context, path string) (image.Image, error)
 }
+
+// WithAuthorization puts the authorization in the context.
+func WithAuthorization(parent context.Context, authorization string) context.Context {
+	return context.WithValue(parent, auth, authorization)
+}
+
+func authorization(ctx context.Context) string {
+	val := ctx.Value(auth)
+	if val == nil {
+		return ""
+	}
+	return val.(string)
+}

pkg/thumbnail/imgsource/webdav.go

@@ -23,11 +23,6 @@ type WebDav struct {
 	baseURL string
 }
 
-const (
-	// WebDavAuth is the parameter name for the autorization token
-	WebDavAuth = "Authorization"
-)
-
 // Get downloads the file from a webdav service
 func (s WebDav) Get(ctx context.Context, file string) (image.Image, error) {
 	u, _ := url.Parse(s.baseURL)
@@ -37,8 +32,8 @@ func (s WebDav) Get(ctx context.Context, file string) (image.Image, error) {
 		return nil, fmt.Errorf("could not get the image \"%s\" error: %s", file, err.Error())
 	}
 
-	auth, ok := authorization(ctx)
-	if !ok {
+	auth := authorization(ctx)
+	if auth == "" {
 		return nil, fmt.Errorf("could not get image \"%s\" error: authorization is missing", file)
 	}
 	req.Header.Add("Authorization", auth)
@@ -59,8 +54,3 @@ func (s WebDav) Get(ctx context.Context, file string) (image.Image, error) {
 	}
 	return img, nil
 }
-
-func authorization(ctx context.Context) (string, bool) {
-	auth, ok := ctx.Value(WebDavAuth).(string)
-	return auth, ok
-}