refactor: append links instead of restting previous one

Respect previously added links as this header can be used by other
components

middleware/sunset.go

@@ -7,19 +7,15 @@ import (
 
 // Sunset set Deprecation/Sunset header to response
 // This can be used to enable Sunset in a route or a route group
-// For more at: https://www.rfc-editor.org/rfc/rfc8594.html
+// For more: https://www.rfc-editor.org/rfc/rfc8594.html
 func Sunset(sunsetAt time.Time, links ...string) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			if !sunsetAt.IsZero() {
 				w.Header().Set("Sunset", sunsetAt.Format(http.TimeFormat))
 				w.Header().Set("Deprecation", sunsetAt.Format(http.TimeFormat))
 
-				for i, link := range links {
-					if i == 0 {
-						w.Header().Set("Link", link)
-						continue
-					}
+				for _, link := range links {
 					w.Header().Add("Link", link)
 				}
 			}