func (c *Conn) Begin() (*Tx, error) {
	return c.begin("")
}
Begin starts a transaction with the default isolation level for the current
connection. To use a specific isolation level see BeginIso.
package pgx
import (
	"errors"
	"fmt"
)
const (
	Serializable    = "serializable"
	RepeatableRead  = "repeatable read"
	ReadCommitted   = "read committed"
	ReadUncommitted = "read uncommitted"
)
const (
	TxStatusInProgress      = 0
	TxStatusCommitFailure   = -1
	TxStatusRollbackFailure = -2
	TxStatusCommitSuccess   = 1
	TxStatusRollbackSuccess = 2
)
var ErrTxClosed = errors.New("tx is closed")
var ErrTxCommitRollback = errors.New("commit unexpectedly resulted in rollback")