Selected Go-internal packages factored out from the standard library (binaries)

 The go-internal repository factors out an opinionated selection of
 internal packages and functionality from the Go standard library.
 Currently this consists mostly of packages and testing code from
 within the Go tool implementation.
 .
 Included are the following:
 .
  * dirhash: calculate hashes over directory trees the same way
             that the Go tool does.
  * goproxytest: a GOPROXY implementation designed for test use.
  * gotooltest: Use the Go tool inside test scripts (see testscript below).
  * imports: list of known architectures and OSs, and support for reading
             import statements.
  * modfile: read and write go.mod files while preserving formatting
             and comments.
  * module: module paths and versions.
  * par: do work in parallel.
  * semver: semantic version parsing.
  * testenv: information on the current testing environment.
  * testscript: script-based testing based on txtar files.
  * txtar: simple text-based file archives for testing.
 .
 This package contains the compiled binaries, namely testscript,
 txtar-addmod, txtar-c and txtar-goproxy.