Bump golangci-lint and (max) Go versions (#219)

Lint is failing with some inscrutable panic (on a commit with no code
changes). Let's try bumping the version in case they fixed it.

Additionally, the new version's github action uses Go 1.19, which means
it pulls in gofmt updates to match the new [doc-comment formatting rules][1].
So I added Go 1.19 to our list of versions to test (fixes #216)
and updated some of our doc-comments to format better in the
new world (mostly using the new link syntax).

[1]: https://go.dev/doc/comment

Test plan: make lint

.github/workflows/go.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '1.16', '1.17', '1.18' ]
+        go: [ '1.16', '1.17', '1.18', '1.19' ]
 
     steps:
     - name: Set up Go
@@ -42,4 +42,4 @@ jobs:
     - name: Run lint
       uses: golangci/golangci-lint-action@v2
       with:
-        version: v1.45   # should match internal/lint/go.mod
+        version: v1.48   # should match internal/lint/go.mod