.github: fix Go version for @latest dependency tests

Author: FiloSottile

.github/workflows/test.yml

@@ -35,6 +35,7 @@ jobs:
             curl --fail --location --remote-name https://github.com/Orange-OpenSource/hurl/releases/download/4.1.0/hurl_4.1.0_amd64.deb
             sudo apt-get install -y ./hurl_4.1.0_amd64.deb
             if [ "${{ matrix.deps }}" = "latest" ]; then
+              go env -w GOTOOLCHAIN=auto
               go get -u -t ./...
             fi
             go test ./...