Update dependencies

[dmke]

Looks like "renovate" doesn't perform two critical steps:

• it doesn't run go mod tidy (Update module github.com/spf13/viper to v1.11.0 #29 did accumulate dependencies in go.sum)
• it doesn't update dependencies (at least not all, this commit includes 7 minor updates)

For parity with the Dockerfile, this PR updated go.mod to use Go 1.18+ as well. This has the extra benefit of automatically separating direct and indirect dependencies.

[mraerino]

Thanks! I think renovate only updates direct dependencies