golang-github-nebulouslabs-errors-dev 0.0~git20170430.98e1f05-1 (i386 binary) in ubuntu hirsute

 The errors package is an extension of and drop in replacement for the
 standard library errors package. Multiple errors can be composed into a
 single error with the Compose function, or a single error can be
 extended by adding context using the Extend function. The result can be
 checked for the presence of a specific error using Contains. If any of
 the underlying composed or extended errors or extensions match,
 Contains will return true.
 .
 This package is especially beneficial during testing, where you may wish
 to check for presence of a specific error, but that specific error may
 be extending another error or may have been extended by another function
 somewhere else in the call stack.