use HttpHandler type

server/handler/internal.go

@@ -7,11 +7,13 @@ import (
 	"time"
 )
 
+type HttpHandler func(http.ResponseWriter, *http.Request)
+
 func Exit(_ http.ResponseWriter, _ *http.Request) {
 	os.Exit(0)
 }
 
-func CreateVersionHandler() func(w http.ResponseWriter, r *http.Request) {
+func CreateVersionHandler() HttpHandler {
 	startTime := time.Now().Unix()
 	return func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintf(w, "%d\n", startTime)

server/handler/sync.go

@@ -11,7 +11,7 @@ type Value struct {
 	Value int
 }
 
-func SyncFactory(obs observer.Property) func(http.ResponseWriter, *http.Request) {
+func SyncFactory(obs observer.Property) HttpHandler {
 	return func(w http.ResponseWriter, r *http.Request) {
 		refId, err := strconv.Atoi(r.URL.Query().Get("ref"))
 		if err != nil {