fix https://github.com/kataras/iris/issues/1608 with the help of @AlbinoGeek for monitoring and together found the source of the problem

_examples/mvc/authenticated-controller/main.go

@@ -16,6 +16,7 @@ import (
 
 func main() {
 	app := newApp()
+	// app.UseRouter(iris.Compression)
 	app.Logger().SetLevel("debug")
 
 	// Open a client, e.g. Postman and visit the below endpoints.

aliases.go

@@ -238,6 +238,9 @@ func (p *prefixedDir) Open(name string) (http.File, error) {
 var (
 	// Compression is a middleware which enables
 	// writing and reading using the best offered compression.
+	// Usage:
+	// app.Use (for matched routes)
+	// app.UseRouter (for both matched and 404s or other HTTP errors).
 	Compression = func(ctx Context) {
 		ctx.CompressWriter(true)
 		ctx.CompressReader(true)

context/compress.go

@@ -345,3 +345,15 @@ func (w *CompressResponseWriter) WriteTo(dest io.Writer, p []byte) (int, error)
 	cw.Close()
 	return n, err
 }
+
+// Reset implements the ResponseWriterReseter interface.
+func (w *CompressResponseWriter) Reset() bool {
+	if w.Disabled {
+		// If it's disabled then the underline one is responsible.
+		rs, ok := w.ResponseWriter.(ResponseWriterReseter)
+		return ok && rs.Reset()
+	}
+
+	w.CompressWriter.Reset(w.ResponseWriter)
+	return true
+}

core/router/api_builder.go

@@ -121,6 +121,7 @@ func (repo *repository) register(route *Route, rule RouteRegisterRule) (*Route,
 var defaultOverlapFilter = func(ctx *context.Context) bool {
 	if ctx.IsStopped() {
 		// It's stopped and the response can be overridden by a new handler.
+		// An exception of compress writer, which does not implement Reseter (and it shouldn't):
 		rs, ok := ctx.ResponseWriter().(context.ResponseWriterReseter)
 		return ok && rs.Reset()
 	}