Ensure proxy connection is closed in proxyRaw function

(#2837)

Author: kumapower17

middleware/proxy.go

@@ -158,6 +158,7 @@ func proxyRaw(t *ProxyTarget, c echo.Context, config ProxyConfig) http.Handler {
 c.Set("_error", echo.NewHTTPError(http.StatusBadGateway, fmt.Sprintf("proxy raw, dial error=%v, url=%s", err, t.URL)))
 return
 }
+defer out.Close()
 
 // Write header
 err = r.Write(out)