Series of operations on an environment performed atomically.
A transaction handle. A transaction may be read-only or read-write.
go perm env f runs a transaction with
perm read/write permissions in
f txn will receive the transaction handle. All changes to the environment
env done using the transaction handle will be persisted to the environment only when
f returns. After
f returned, the transaction handle is invalid and should therefore not be leaked outside
val abort : _ t -> _
abort txn aborts transaction
txn and the current
go function, which will return