Automatic model migration for Postgres

migration.go

func migrate(db *pg.DB, tables ...[]T) chan error {
	errfeed := make(chan error)

	go func() {
		for _, model := range tables {
			err := db.CreateTable(model, &orm.CreateTableOptions{IfNotExists: true})
			if err != nil {
				errfeed <- err
				continue
			}

			table := orm.GetTable(reflect.TypeOf(model).Elem())
			columns := make([]string, 0, len(table.Fields))
			for _, field := range table.Fields {
				columns = append(columns, `"`+field.SQLName+`" `+field.SQLType)
			}

			err = db.RunInTransaction(func(tx *pg.Tx) error {
				for i, column := range columns {
					query := fmt.Sprintf("ALTER TABLE %s ADD COLUMN IF NOT EXISTS %s",
						table.Name, column)

					defaultExpr := table.Fields[i].Default
					if defaultExpr != "" {
						query += " DEFAULT (" + string(defaultExpr) + ")"
					}

					if pgTag, ok := table.Fields[i].Field.Tag.Lookup("pg"); ok {
						if strings.Contains(pgTag, "notnull") {
							query += " NOT NULL"
						}
					}

					_, err := tx.Exec(query)
					if err != nil {
						fmt.Println(query)
						errfeed <- err
						continue
					}
				}

				return nil
			})

			if err != nil {
				errfeed <- err
			}
		}

		close(errfeed)
	}()

	return errfeed
}