Module Mirror and Checksum Database Launched

I like the simple plain text signing format for the API calls. For example: https://sum.golang.org/lookup/go.etcd.io/etcd@v0.4.0

Is signed with:

  — sum.golang.org Az3grobHchAJWrV4M34o1kLnZV4vrGSfFA+2Q9VClbmWqBjsnN4GzK1xB1RaYGSo0jIjWH9GDcR3Tja5sadw2ESoKwg=

The format is documented here: https://godoc.org/golang.org/x/mod/sumdb/note