add static assets caching

internal/server/middleware.go

@@ -0,0 +1,44 @@
+package server
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/labstack/echo/v4"
+	"github.com/rjNemo/underscore"
+)
+
+const (
+	defaultTTL = 2592000 // 1 month
+)
+
+// CachingMiddleware adds caching headers.
+// ttl is the max age of the cache in seconds. If ttl is 0, the default value wil be used.
+func CachingMiddleware(ttl int, fileTypes ...string) echo.MiddlewareFunc {
+	if ttl == 0 {
+		ttl = defaultTTL
+	}
+	return func(next echo.HandlerFunc) echo.HandlerFunc {
+		return func(c echo.Context) error {
+			shouldCache := underscore.Any(fileTypes, func(v string) bool {
+				return strings.HasSuffix(c.Request().RequestURI, fmt.Sprintf(".%s", v))
+			})
+
+			if shouldCache {
+				s := strings.Split(c.Request().RequestURI, "/")
+				etag := s[len(s)-1]
+
+				c.Response().Header().Set("Etag", etag)
+				c.Response().Header().Set("Cache-Control", fmt.Sprintf("max-age=%d", ttl))
+				if match := c.Request().Header.Get("If-None-Match"); match != "" {
+					if strings.Contains(match, etag) {
+						return c.NoContent(http.StatusNotModified)
+					}
+				}
+			}
+
+			return next(c)
+		}
+	}
+}

internal/server/server.go

@@ -102,6 +102,7 @@ func NewRouter(fs embed.FS, debug bool, secret string, origins []string) *echo.E
 	e.Use(middleware.CORSWithConfig(middleware.CORSConfig{AllowOrigins: origins}))
 	e.Use(sentryecho.New(sentryecho.Options{}))
 	e.Use(SentryTracingMiddleware)
+	e.Use(CachingMiddleware(0, "js", "css", "png", "ico"))
 	e.Use(session.Middleware(sessions.NewCookieStore([]byte(secret))))
 	// static assets
 	e.StaticFS("/static", echo.MustSubFS(fs, "assets"))