code: func (m *moduleMgr) readModuleManifestSnapshot() error {
  	r, err := m.FS.Open(m.manifestSnapshotPath())
  	if err != nil {
  		if os.IsNotExist(err) {
  			// We'll treat a missing file as an empty manifest
  			m.manifest = make(modsdir.Manifest)
  			return nil
  		}
  		return err
  	}
  
  	m.manifest, err = modsdir.ReadManifestSnapshot(r)
  	return err
  }
docs: // readModuleManifestSnapshot loads a manifest snapshot from the filesystem.