go mod: declare module version v2

Our git version is v2+ for some time now, but go.mod
still declared v1. Hopefully making both match makes
https://pkg.go.dev/github.com/rfjakob/gocryptfs/v2 work.

All the import paths have been fixed like this:

  find . -name \*.go | xargs sed -i s%github.com/rfjakob/gocryptfs/%github.com/rfjakob/gocryptfs/v2/%

1 files changed, 1 insertions, 1 deletions

diff --git a/go.mod b/go.mod
index 34491bf..12c5e1a 100644
--- a/go.mod
+++ b/go.mod
@@ -1,4 +1,4 @@
-module github.com/rfjakob/gocryptfs
+module github.com/rfjakob/gocryptfs/v2
 
 go 1.16