move genqlient Go module to 1.20 (#318)

gqlgen's module supports Go 1.20+, and I suggest that genqlient should
also do so.

Go 1.20 was released more than 1 year ago (01 Feb 2023), and support
ended on 06 Feb 2024.
Each major Go release is supported until there are two newer major
releases.

In the past, we have only prolonged gqlgen/genqlient support for older
Go when AppEngine Go was mired in the past.

Currently, [Appengine no longer supports Go
1.18](https://cloud.google.com/appengine/docs/standard/go/release-notes),
and supports up to Go 1.21.

I will wait for possible objections for a few days before merging this
PR. I also expect that we would want to cut a new release of genqlient
either before or after merging this PR.

Signed-off-by: Steve Coffman <[email protected]>

---------

Signed-off-by: Steve Coffman <[email protected]>

.github/workflows/go.yml

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

docs/CHANGELOG.md

@@ -20,10 +20,12 @@ When releasing a new version:
 
 <!-- Add new changes in this section! -->
 
-Note that genqlient is now tested through Go 1.22.
+Note that genqlient is now tested from Go 1.20 through Go 1.22.
 
 ### Breaking changes:
 
+- genqlient now requires Go 1.20 or higher. It may still work with earlier versions, but we aren't explicitly keeping dependency modules to Go 1.18 and lower.
+
 ### New features:
 
 - The new `optional: generic` allows using a generic type to represent optionality. See the [documentation](genqlient.yaml) for details.

go.mod

@@ -1,6 +1,6 @@
 module github.com/Khan/genqlient
 
-go 1.18
+go 1.20
 
 require (
 	github.com/99designs/gqlgen v0.17.44