You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: uuid_test.go
    path of file: ./repos/clickhouse-go/tests/std
    
    the code of the file until where you have to start completion: // Licensed to ClickHouse, Inc. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownershi
    
func TestStdNullableUUID(t *testing.T) {
	env, err := GetStdTestEnvironment()
	require.NoError(t, err)
	useSSL, err := strconv.ParseBool(clickhouse_tests.GetEnv("CLICKHOUSE_USE_SSL", "false"))
	require.NoError(t, err)
	dsns := map[string]string{"Native": fmt.Sprintf("clickhouse://%s:%d?username=%s&password=%s", env.Host, env.Port, env.Username, env.Password),
		"Http": fmt.Sprintf("http://%s:%d?username=%s&password=%s&session_id=session", env.Host, env.HttpPort, env.Username, env.Password)}
	if useSSL {
		dsns = map[string]string{"Native": fmt.Sprintf("clickhouse://%s:%d?username=%s&password=%s&secure=true", env.Host, env.SslPort, env.Username, env.Password),
			"Http": fmt.Sprintf("https://%s:%d?username=%s&password=%s&session_id=session&secure=true", env.Host, env.HttpsPort, env.Username, env.Password)}
	}
	for name, dsn := range dsns {
		t.Run(fmt.Sprintf("%s Protocol", name), func(t *testing.T) {
			conn, err := GetConnectionFromDSN(dsn)
			require.NoError(t, err)
			const ddl = `
					CREATE TEMPORARY TABLE test_uuid (
						  Col1 Nullable(UUID)
						, Col2 Nullable(UUID)
					)
				`
			defer func() {
				conn.Exec("DROP TABLE test_uuid")
			}()
			_, err = conn.Exec(ddl)
			require.NoError(t, err)
			scope, err := conn.Begin()
			require.NoError(t, err)
			batch, err := scope.Prepare("INSERT INTO test_uuid")
			require.NoError(t, err)
			var (
				col1Data = uuid.New()
				col2Data = uuid.New()
			)
			_, err = batch.Exec(col1Data, col2Data)
			require.NoError(t, err)
			require.NoError(t, scope.Commit())
			var (
				col1 *uuid.UUID
				col2 *uuid.UUID
			)
			require.NoError(t, conn.QueryRow("SELECT * FROM test_uuid").Scan(&col1, &col2))
			assert.Equal(t, col1Data, *col1)
			assert.Equal(t, col2Data, *col2)
			_, err = conn.Exec("TRUNCATE TABLE test_uuid")
			require.NoError(t, err)
			scope, err = conn.Begin()
			require.NoError(t, err)
			batch, err = scope.Prepare("INSERT INTO test_uuid")
			require.NoError(t, err)
			col1Data = uuid.New()
			_, err = batch.Exec(col1Data, nil)
			require.NoError(t, err)
			require.NoError(t, scope.Commit())
			{
				var (
					col1 *uuid.UUID
					col2 *uuid.UUID
				)
				require.NoError(t, conn.QueryRow("SELECT * FROM test_uuid").Scan(&col1, &col2))
				require.Nil(t, col2)
				assert.Equal(t, col1Data, *col1)
			}
		})
	}
}