Test and lint against Go 1.19

Add Go 1.19 to the test matrix, and switch linting to Go 1.19 since we
prefer to lint with the latest stable release.

With Go 1.19, we need to:

- Update tools dependencies
- Fix any use of ioutil
- gofmt all files to match new godoc format

.github/workflows/go.yml

@@ -13,9 +13,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: ["1.17.x", "1.18.x"]
+        go: ["1.17.x", "1.18.x", "1.19.x"]
         include:
-        - go: 1.18.x
+        - go: 1.19.x
           latest: true
 
     steps:

appendinvoke_example_test.go

@@ -22,7 +22,6 @@ package multierr_test
 
 import (
 	"fmt"
-	"io/ioutil"
 	"log"
 	"os"
 	"path/filepath"
@@ -37,7 +36,7 @@ func ExampleAppendInvoke() {
 }
 
 func run() (err error) {
-	dir, err := ioutil.TempDir("", "multierr")
+	dir, err := os.MkdirTemp("", "multierr")
 	// We create a temporary directory and defer its deletion when this
 	// function returns.
 	//