(#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.go

@@ -0,0 +1,64 @@
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	app := newApp()
+	app.Logger().SetLevel("debug")
+	app.Listen(":8080")
+}
+
+func newApp() *iris.Application {
+	app := iris.New()
+	// HERE and you are ready to GO:
+	app.Use(iris.Compress, iris.CompressReader)
+
+	app.Get("/", send)
+	app.Post("/", receive)
+
+	return app
+}
+
+type payload struct {
+	Username string `json:"username"`
+}
+
+func send(ctx iris.Context) {
+	ctx.JSON(payload{
+		Username: "Makis",
+	})
+}
+
+func receive(ctx iris.Context) {
+	var p payload
+	if err := ctx.ReadJSON(&p); err != nil {
+		ctx.Application().Logger().Debugf("ReadJSON: %v", err)
+	}
+
+	ctx.WriteString(p.Username)
+}
+
+/* Manually:
+func enableCompression(ctx iris.Context) {
+	// Enable writing using compression (deflate, gzip, brotli, snappy, s2):
+	err := ctx.Compress(true)
+	if err != nil {
+		ctx.Application().Logger().Debugf("writer: %v", err)
+		// if you REQUIRE server to SEND compressed data then `return` here.
+		// return
+	}
+
+	// Enable reading and binding request's compressed data:
+	err = ctx.CompressReader(true)
+	if err != nil &&
+		// on GET we don't expect writing with gzip from client
+		ctx.Method() != iris.MethodGet  {
+		ctx.Application().Logger().Debugf("reader: %v", err)
+		// if you REQUIRE server to RECEIVE only
+		// compressed data then `return` here.
+		// return
+	}
+
+	ctx.Next()
+}
+*/