code: func FileBase64(baseDir string, path cty.Value) (cty.Value, error) {
  	fn := MakeFileFunc(baseDir, true)
  	return fn.Call([]cty.Value{path})
  }
docs: // FileBase64 reads the contents of the file at the given path.
  //
  // The bytes from the file are encoded as base64 before returning.
  //
  // The underlying function implementation works relative to a particular base
  // directory, so this wrapper takes a base directory string and uses it to
  // construct the underlying function before calling it.