(#1554) Add support for all common compressions (write and read)

- Remove the context.Context interface and export the *context, the iris.Context now points to the pointer\nSupport compression and rate limiting in the FileServer\nBit of code organisation


Former-commit-id: ad1c61bf968059510c6be9e7f2cceec7da70ba17

_examples/compression/main_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"encoding/json"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/kataras/iris/v12/context"
+	"github.com/kataras/iris/v12/httptest"
+)
+
+func TestCompression(t *testing.T) {
+	app := newApp()
+	e := httptest.New(t, app)
+
+	var expectedReply = payload{Username: "Makis"}
+	body := e.GET("/").WithHeader(context.AcceptEncodingHeaderKey, context.GZIP).Expect().
+		Status(httptest.StatusOK).
+		ContentEncoding(context.GZIP).
+		ContentType(context.ContentJSONHeaderValue).Body().Raw()
+
+	// Note that .Expect() consumes the response body
+	// and stores it to unexported "contents" field
+	// therefore, we retrieve it as string and put it to a new buffer.
+	r := strings.NewReader(body)
+	cr, err := context.NewCompressReader(r, context.GZIP)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cr.Close()
+
+	var got payload
+	if err = json.NewDecoder(cr).Decode(&got); err != nil {
+		t.Fatal(err)
+	}
+
+	if !reflect.DeepEqual(expectedReply, got) {
+		t.Fatalf("expected %#+v but got %#+v", expectedReply, got)
+	}
+}