reorganization of _examples and add some new examples such as iris+groupcache+mysql+docker

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/response-writer/stream-writer/main.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt" // just an optional helper
+	"io"
+	"time" // showcase the delay
+
+	"github.com/kataras/iris/v12"
+)
+
+func main() {
+	app := iris.New()
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.ContentType("text/html")
+		ctx.Header("Transfer-Encoding", "chunked")
+		i := 0
+		ints := []int{1, 2, 3, 5, 7, 9, 11, 13, 15, 17, 23, 29}
+		// Send the response in chunks and wait for half a second between each chunk.
+		ctx.StreamWriter(func(w io.Writer) bool {
+			fmt.Fprintf(w, "Message number %d<br>", ints[i])
+			time.Sleep(500 * time.Millisecond) // simulate delay.
+			if i == len(ints)-1 {
+				return false // close and flush
+			}
+			i++
+			return true // continue write
+		})
+	})
+
+	type messageNumber struct {
+		Number int `json:"number"`
+	}
+
+	app.Get("/alternative", func(ctx iris.Context) {
+		ctx.ContentType("application/json")
+		ctx.Header("Transfer-Encoding", "chunked")
+		i := 0
+		ints := []int{1, 2, 3, 5, 7, 9, 11, 13, 15, 17, 23, 29}
+		// Send the response in chunks and wait for half a second between each chunk.
+		for {
+			ctx.JSON(messageNumber{Number: ints[i]})
+			ctx.WriteString("\n")
+			time.Sleep(500 * time.Millisecond) // simulate delay.
+			if i == len(ints)-1 {
+				break
+			}
+			i++
+			ctx.ResponseWriter().Flush()
+		}
+	})
+
+	app.Listen(":8080")
+}