Release 1.9.0

For 2.0.0 we need the change the module to /v2, including the Generator (postponing this for now).

GitHub Actions go.yml: have a matrix for Go versions

Merge branch '141-get-many-32-bit' into dev

Make TestPutInMemoryDB work with Go versions before 1.13

Merge branch 'c-v0.18'

1.6.1

Prepare 1.6.0

prepare v1.5.0

increase version to v1.4.0

prepare 1.3.0 release