Is your feature request related to a problem? Please describe.
Parsing fails when trying to migrate to Spanner DB with generated columns:

deletableTime TIMESTAMP AS (IF(deletable, created, NULL)) STORED,

outputs:

error: :9: got "(" while expecting ")"

Describe the solution you'd like
Update go modules: cloud.google.com/go/spanner.

Checking out the source and running:

go get -u cloud.google.com/go/spanner
go mod tidy

After that change, migrate can be applied without error.

Describe alternatives you've considered
Current workaround is to clone project and update dependencies locally.

Additional context