I can't find any "starter documentation" on x/hep/rootio

Created by: jpivarski

The code snippet at the top of the API documentation is very terse and contains an error: it reassigns err but the inferred type is (now) different between those two lines.

Having found a "Hello, world" Go program on the web to edit, I wrote the following:

package main

import "go-hep.org/x/hep/rootio"
import "fmt"

func main() {
  f, err := rootio.Open("~/storage/data/TrackResonanceNtuple_uncompressed.root")
  obj, err2 := f.Get("twoMuon")
  tree := obj.(*rootio.Tree)
  fmt.Printf("entries= %v\n", t.Entries())
}

It fails with

% go build test.go
# command-line-arguments
./test.go:9:14: impossible type assertion:
        *rootio.Tree does not implement rootio.Object (missing Class method)
./test.go:10:31: undefined: t

(I have Go 1.9 and did go get go-hep.org/x/hep/rootio without specifying a version: is it taking master from GitHub or the latest release?)

Is there tutorial-style documentation that I simply haven't found? Are there any minimally working examples? Thanks!