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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/database/mysql/main.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"myapp/api"
+	"myapp/sql"
+
+	"github.com/kataras/iris/v12"
+)
+
+func main() {
+	dsn := fmt.Sprintf("%s:%s@tcp(%s:3306)/%s?parseTime=true&charset=utf8mb4&collation=utf8mb4_unicode_ci",
+		getenv("MYSQL_USER", "user_myapp"),
+		getenv("MYSQL_PASSWORD", "dbpassword"),
+		getenv("MYSQL_HOST", "localhost"),
+		getenv("MYSQL_DATABASE", "myapp"),
+	)
+
+	db, err := sql.ConnectMySQL(dsn)
+	if err != nil {
+		log.Fatalf("error connecting to the MySQL database: %v", err)
+	}
+
+	secret := getenv("JWT_SECRET", "EbnJO3bwmX")
+
+	app := iris.New()
+	subRouter := api.Router(db, secret)
+	app.PartyFunc("/", subRouter)
+
+	addr := fmt.Sprintf(":%s", getenv("PORT", "8080"))
+	app.Listen(addr)
+}
+
+func getenv(key string, def string) string {
+	v := os.Getenv(key)
+	if v == "" {
+		return def
+	}
+
+	return v
+}