go: Add support for Go modules

So that building and using ZODB/go works not only in GOPATH mode.

go/go.mod

+module lab.nexedi.com/kirr/neo/go
+
+go 1.14
+
+require (
+	github.com/DataDog/czlib v0.0.0-20210322182103-8087f4e14ae7
+	github.com/cznic/strutil v0.0.0-20181122101858-275e90344537
+	github.com/fsnotify/fsnotify v1.7.0
+	github.com/golang/glog v1.2.2
+	github.com/kisielk/og-rek v1.2.0
+	github.com/kylelemons/godebug v1.1.0
+	github.com/philhofer/fwd v1.1.3-0.20240612014219-fbbf4953d986
+	github.com/pkg/errors v0.9.1
+	github.com/shamaton/msgpack v1.2.1
+	github.com/someonegg/gocontainer v1.0.0
+	github.com/stretchr/testify v1.9.0
+	github.com/tinylib/msgp v1.2.0
+	lab.nexedi.com/kirr/go123 v0.0.0-20240626173136-48920809d24c
+)
+
+require (
+	crawshaw.io/sqlite v0.3.2 // indirect
+	github.com/cznic/mathutil v0.0.0-20181122101859-297441e03548 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)