fix: Add all go.mod files

What's Changed

• build: Improve testing by @markvl-sbp in #105
• fix: [#95] Add all go.mod files by @markvl-sbp in #106
• fix: [#95] Run go mod tidy in all directories with go.mod files by @markvl-sbp in #107
• build: Start using pyproject.toml by @markvl-sbp in #108

Full Changelog: v0.3.0...v0.3.1