Fix go transaction examples for databases with 'ddl in tran'

[ntnn]

Description

Some databases do not have the ddl in tran database option set, which would cause these examples to fail as no tables can be created. Since the examples should be option-agnostic the statements to create the relevant table are moved above the transaction opening.

I've also fixed some style issues while I was at it.

Related issues

Link any related issues here.

Tests

• [x] make lint
• [x] make test-go / make test-cgo
• [x] make integration-go / make integration-cgo