Add tests on Go 1.22, and upgrade x/tools to make them work (#315)

I guess our x/tools was too old? I'm unclear on how x/tools versioning
works with language versioning. Anyway, now it all works. Fixes #312.

I have:
- [x] Written a clear PR title and description (above)
- [x] Signed the [Khan Academy CLA](https://www.khanacademy.org/r/cla)
- [x] Added tests covering my changes, if applicable (n/a)
- [x] Included a link to the issue fixed, if applicable
- [x] Included documentation, for new features (n/a)
- [x] Added an entry to the changelog

.github/workflows/go.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '1.18', '1.19', '1.20', '1.21' ]
+        go: [ '1.18', '1.19', '1.20', '1.21', '1.22' ]
 
     steps:
     - name: Set up Go

docs/CHANGELOG.md

@@ -20,6 +20,8 @@ When releasing a new version:
 
 <!-- Add new changes in this section! -->
 
+Note that genqlient is now tested through Go 1.22.
+
 ### Breaking changes:
 
 ### New features:

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/bradleyjkemp/cupaloy/v2 v2.6.0
 	github.com/stretchr/testify v1.8.2
 	github.com/vektah/gqlparser/v2 v2.5.8
-	golang.org/x/tools v0.9.3
+	golang.org/x/tools v0.18.0
 	gopkg.in/yaml.v2 v2.4.0
 )
 
@@ -20,7 +20,6 @@ require (
 	github.com/hashicorp/golang-lru/v2 v2.0.3 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	golang.org/x/mod v0.10.0 // indirect
-	golang.org/x/sys v0.8.0 // indirect
+	golang.org/x/mod v0.15.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )