go: add a simple caching middleware for assets

app/routes.go

@@ -37,7 +37,7 @@ func (a *App) SetupRoutes() {
 	)
 	// alternative:
 	// e.GET("/static/*", echo.WrapHandler(http.StripPrefix("/static/", assets)))
-	e.GET("/assets/*", echo.WrapHandler(http.StripPrefix("/assets/", assets)))
+	e.GET("/assets/*", echo.WrapHandler(http.StripPrefix("/assets/", assets)), handlers.MiddlewareCache)
 
 	e.GET("/healthz", handlers.Healthz())
 	e.GET("/health", handlers.Healthz())

handlers/middleware.go

@@ -6,6 +6,7 @@ package handlers
 import (
 	"context"
 	"net/http"
+	"strings"
 
 	moduser "git.dotya.ml/mirre-mt/pcmt/modules/user"
 	"github.com/labstack/echo-contrib/session"
@@ -97,3 +98,24 @@ func MiddlewareSession(next echo.HandlerFunc) echo.HandlerFunc {
 		return next(c)
 	}
 }
+
+var cacheExtensions = [2]string{".png", ".svg"}
+
+func MiddlewareCache(next echo.HandlerFunc) echo.HandlerFunc {
+	return func(c echo.Context) error {
+		cache := false
+
+		for _, v := range cacheExtensions {
+			if strings.HasSuffix(c.Request().URL.Path, v) {
+				cache = true
+				break
+			}
+		}
+
+		if cache {
+			c.Response().Header().Set(echo.HeaderCacheControl, "300")
+		}
+
+		return next(c)
+	}
+}