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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/request-referrer/main.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+)
+
+func main() {
+	app := iris.New()
+
+	app.Get("/", func(ctx iris.Context) {
+		// GetReferrer extracts and returns the information from the "Referrer" header as specified
+		// in https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy or by the URL query parameter "referrer".
+		r := ctx.GetReferrer()
+		switch r.Type {
+		case iris.ReferrerSearch:
+			ctx.Writef("Search %s: %s\n", r.Label, r.Query)
+			ctx.Writef("Google: %s\n", r.GoogleType)
+		case iris.ReferrerSocial:
+			ctx.Writef("Social %s\n", r.Label)
+		case iris.ReferrerIndirect:
+			ctx.Writef("Indirect: %s\n", r.URL)
+		}
+	})
+
+	// http://localhost:8080?referrer=https://twitter.com/Xinterio/status/1023566830974251008
+	// http://localhost:8080?referrer=https://www.google.com/search?q=Top+6+golang+web+frameworks&oq=Top+6+golang+web+frameworks
+	app.Listen(":8080")
+}