multi: Build and doco updates for Go 1.19.

[davecgh]

This consists of several commit to update the CI and documentation for Go 1.19. It also takes the opportunity to bump to the latest linter and action versions.

In particular:

• main: Go 1.19 doc comment formatting.
• build: Update to latest action versions.
  • actions/setup-go@84cbf8094393cdc5fe1fe1671ff2647332956b1a #v3.2.1
  • actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b #v3.0.2
• build: Update golangci-lint to v1.48.0.
• build: Test against Go 1.19 and remove Go 1.17 accordingly.
• docs: Update README.md for Go 1.19 and rel 1.7.4.

[davecgh]

This will need to wait until the linter is updated to work with Go 1.19.