fix hidden errors

[matoubidou]

Hello,

thank for this neat library! Just stumbled over some swallowed errors. IMHO named returned values are always a little bit dangerous. In your case the returned named error was not set as a new one was defined, i.e.:

func foo() (err error) {
  err := barReturningAnErrror()
  if err != nil {
    return
  }
}

will not return anything. Hopefully I got all occurrences of the issue.

Best regards

_{Mathias Zeller mathias.zeller@mercedes-benz.com Mercedes-Benz Tech Innovation GmbH (ProviderInformation)}

[matoubidou]

Closing in favor of #163 (re-submitted from new account)