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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/database/mysql/sql/mysql.go

@@ -0,0 +1,123 @@
+package sql
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	_ "github.com/go-sql-driver/mysql" // lint: mysql driver.
+)
+
+// MySQL holds the underline connection of a MySQL (or MariaDB) database.
+// See the `ConnectMySQL` package-level function.
+type MySQL struct {
+	Conn *sql.DB
+}
+
+var _ Database = (*MySQL)(nil)
+
+var (
+	// DefaultCharset default charset parameter for new databases.
+	DefaultCharset = "utf8mb4"
+	// DefaultCollation default collation parameter for new databases.
+	DefaultCollation = "utf8mb4_unicode_ci"
+)
+
+// ConnectMySQL returns a new ready to use MySQL Database instance.
+// Accepts a single argument of "dsn", i.e:
+// username:password@tcp(localhost:3306)/myapp?parseTime=true&charset=utf8mb4&collation=utf8mb4_unicode_ci
+func ConnectMySQL(dsn string) (*MySQL, error) {
+	conn, err := sql.Open("mysql", dsn)
+	if err != nil {
+		return nil, err
+	}
+	err = conn.Ping()
+	if err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	return &MySQL{
+		Conn: conn,
+	}, nil
+}
+
+// CreateDatabase executes the CREATE DATABASE query.
+func (db *MySQL) CreateDatabase(database string) error {
+	q := fmt.Sprintf("CREATE DATABASE %s DEFAULT CHARSET = %s COLLATE = %s;", database, DefaultCharset, DefaultCollation)
+	_, err := db.Conn.Exec(q)
+	return err
+}
+
+// Drop executes the DROP DATABASE query.
+func (db *MySQL) Drop(database string) error {
+	q := fmt.Sprintf("DROP DATABASE %s;", database)
+	_, err := db.Conn.Exec(q)
+	return err
+}
+
+// Select performs the SELECT query for this database (dsn database name is required).
+func (db *MySQL) Select(ctx context.Context, dest interface{}, query string, args ...interface{}) error {
+	rows, err := db.Conn.QueryContext(ctx, query, args...)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+
+	if scannable, ok := dest.(Scannable); ok {
+		return scannable.Scan(rows)
+	}
+
+	if !rows.Next() {
+		return ErrNoRows
+	}
+	return rows.Scan(dest)
+
+	/* Uncomment this and pass a slice if u want to see reflection powers <3
+	v, ok := dest.(reflect.Value)
+	if !ok {
+		v = reflect.Indirect(reflect.ValueOf(dest))
+	}
+
+	sliceTyp := v.Type()
+
+	if sliceTyp.Kind() != reflect.Slice {
+		sliceTyp = reflect.SliceOf(sliceTyp)
+	}
+
+	sliceElementTyp := deref(sliceTyp.Elem())
+	for rows.Next() {
+		obj := reflect.New(sliceElementTyp)
+		obj.Interface().(Scannable).Scan(rows)
+		if err != nil {
+			return err
+		}
+
+		v.Set(reflect.Append(v, reflect.Indirect(obj)))
+	}
+	*/
+}
+
+// Get same as `Select` but it moves the cursor to the first result.
+func (db *MySQL) Get(ctx context.Context, dest interface{}, query string, args ...interface{}) error {
+	rows, err := db.Conn.QueryContext(ctx, query, args...)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+	if !rows.Next() {
+		return ErrNoRows
+	}
+
+	if scannable, ok := dest.(Scannable); ok {
+		return scannable.Scan(rows)
+	}
+
+	return rows.Scan(dest)
+}
+
+// Exec executes a query. It does not return any rows.
+// Use the first output parameter to count the affected rows on UPDATE, INSERT, or DELETE.
+func (db *MySQL) Exec(ctx context.Context, query string, args ...interface{}) (sql.Result, error) {
+	return db.Conn.ExecContext(ctx, query, args...)
+}