Use Go 1.22 in GitHub Actions.

Author: bobg

.github/workflows/go.yml

@@ -15,7 +15,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v2
       with:
-        go-version: 1.16
+        go-version: 1.22
 
     - name: Unit tests
       run: go test -v -coverprofile=cover.out ./...

go.mod

@@ -1,5 +1,5 @@
 module github.com/bobg/merkle/v2
 
-go 1.14
+go 1.20
 
 require golang.org/x/crypto v0.25.0