How to modify the response from middleware?

[sazzer]

I'm writing some middleware to do simple cache responses. Specifically, it will return an HTTP 304, and will return no body and no content-type header if the if-none-match or if-modified-since request headers match the corresponding etag or last-modified response headers.

All of this is easy enough, except changing the response body. Specifically, what I've got is this:

func cachingMiddleware() echo.MiddlewareFunc {	return func(next echo.HandlerFunc) echo.HandlerFunc {	return func(c echo.Context) error {	ifNoneMatch := c.Request().Header.Get("if-none-match")	ifModifiedSince := c.Request().Header.Get("if-modified-since")	c.Response().Before(func() {	etag := c.Response().Header().Get("etag")	lastModified := c.Response().Header().Get("last-modified")	cacheHit := true	switch {	case ifNoneMatch == "" && ifModifiedSince == "":	// No cache headers!	cacheHit = false	case ifNoneMatch != "" && ifNoneMatch != etag:	// If-None-Match header provided and differs from ETag.	cacheHit = false	case ifModifiedSince != "" && ifModifiedSince != lastModified:	// If-Modified-Since header provided and differs from Last-Modified.	cacheHit = false	}	slog.Debug("Caching result",	"if-none-match", ifNoneMatch,	"if-modified-since", ifModifiedSince,	"etag", etag,	"last-modified", lastModified,	"cacheHit", cacheHit,	)	if cacheHit {	c.Response().Status = http.StatusNotModified	c.Response().Header().Del("content-type")	// TODO: DON'T SEND THE RESPONSE BODY	}	})	result := next(c)	return result	}	} } 

The bit that I can't work out is the "TODO: DON'T SEND THE RESPONSE BODY" bit.

What's the recommended way to achieve this?

Cheers