Restore dropped cfenv module (#88)

go.mod

@@ -7,6 +7,7 @@ require (
 	code.cloudfoundry.org/go-loggregator/v9 v9.0.5
 	github.com/alecthomas/kingpin/v2 v2.3.2
 	github.com/cloudfoundry-community/go-cfclient/v2 v2.0.0
+	github.com/cloudfoundry-community/go-cfenv v1.18.0
 	github.com/cloudfoundry/noaa/v2 v2.2.1-0.20230608172525-8fe94f183391
 	github.com/cloudfoundry/sonde-go v0.0.0-20230606195250-c7c0fdf1ccc4
 	github.com/jarcoal/httpmock v1.3.0
@@ -23,13 +24,15 @@ require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/blang/semver/v4 v4.0.0 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.6.0 // indirect
 	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/gorilla/websocket v1.5.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.16.0 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
+	github.com/mitchellh/mapstructure v1.1.2 // indirect
 	github.com/nxadm/tail v1.4.8 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/prometheus/common v0.44.0 // indirect