Increase coverage so the lib can make the 'awesome-go' list

[kpacha]

We've lost some of the coverage earned at #6 but we were not close to the requirements of https://github.com/avelino/awesome-go/blob/master/CONTRIBUTING.md#quality-standards

Tests, where practical. If the library/program is testable, then coverage should be >= 80% for non-data-related packages and >=90% for data related packages. Notice: the tests will be reviewed too. We will check your coverage manually if your package's coverage is just a benchmark results.