* Removing `go.mod` for the v3-release branch
As discussed in full length here (#17), we have run into issues that forces us to abandon go modules, at least for the `v3.x.x` releases. After this is merged in, we can release a `v3.2.1+incompatible` version, which contains a security fix.
Afterwards, we will work on non-breaking quality of life fixes and then eventually run a `v4` version, which most likely will then support go modules and have a new SIV-style import path.
* Cloning into $GOPATH for GitHub actions
* Providing full test matrix
* Only testing Go version with module support on GitHub actions
* Only testing legacy versions on travis. Will be deprecated in time