Go mod support

[someone1]

As-is, using go mod will fail building this package since it points to v2.0.0 by default of this repository which is the fork of gomodule/redigo. Possibly tagging a new version (e.g. v2.1.0 or something) would fix this. Alternatively, adding full support of go mod would be welcome!

[odeke-em]

Thanks for filing this @someone1! This package at some point is planned to be merged upstream with gomodule/redigo and I've made the original authors aware of it.

In the meantime sure, I'll add support for go mod.

[odeke-em]

I've tagged v2.0.1 https://github.com/opencensus-integrations/redigo/releases/tag/v2.0.1