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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/database/mysql/sql/sql.go

@@ -0,0 +1,40 @@
+package sql
+
+import (
+	"context"
+	"database/sql"
+)
+
+// Database is an interface which a database(sql) should implement.
+type Database interface {
+	Get(ctx context.Context, dest interface{}, q string, args ...interface{}) error
+	Select(ctx context.Context, dest interface{}, q string, args ...interface{}) error
+	Exec(ctx context.Context, q string, args ...interface{}) (sql.Result, error)
+}
+
+// Record should represent a database record.
+// It holds the table name and the primary key.
+// Entities should implement that
+// in order to use the BaseService's methods.
+type Record interface {
+	TableName() string  // the table name which record belongs to.
+	PrimaryKey() string // the primary key of the record.
+}
+
+// Sorted should represent a set of database records
+// that should be rendered with order.
+//
+// It does NOT support the form of
+// column1 ASC,
+// column2 DESC
+// The OrderBy method should return text in form of:
+// column1
+// or column1, column2
+type Sorted interface {
+	SortBy() string // column names separated by comma.
+}
+
+// Scannable for go structs to bind their fields.
+type Scannable interface {
+	Scan(*sql.Rows) error
+}