common logging package for HashiCorp tools

 go-hclog is a package for Go that provides a simple key/value logging
 interface for use in development and production environments.
 .
 It provides logging levels that provide decreased output based upon the
 desired amount of output, unlike the standard library log package.
 .
 It provides Printf style logging of values via hclog.Fmt().
 .
 It provides a human readable output mode for use in development as well
 as JSON output mode for production.