Add Go 1.20 to Travis

- Use golang-ci in go test workflow

Signed-off-by: Sylvain Rabot <sylvain@abstraction.fr>
Signed-off-by: Waldemar Quevedo <wally@nats.io>

.travis.yml

@@ -9,6 +9,8 @@ go:
 # This should be quoted or use .x, but should not be unquoted.
 # Remember that a YAML bare float drops trailing zeroes.
   - "1.19.12"
+  - "1.20.x"
+
 go_import_path: github.com/nats-io/nats-server
 
 addons:
@@ -50,4 +52,4 @@ deploy:
   script: curl -sL http://git.io/goreleaser | bash
   on:
     tags: true
-    condition: ($TRAVIS_GO_VERSION =~ 1.19) && ($TEST_SUITE = "compile")
+    condition: ($TRAVIS_GO_VERSION =~ 1.20) && ($TEST_SUITE = "compile")