chore(gha): fix macos action/setup-go@v4 cache miss.

Set the same Go version as specified in the `go.mod`
because of the issue below:
- actions/setup-go#424

Additionally, the rand.Seed() was updated to use
rand.New(rand.NewSource(seed)) because the former was
removed from Go1.20.

Signed-off-by: Tiago Natel <t.nateldemoura@gmail.com>

cmd/terramate/cli/cloud_credential_google.go

@@ -148,13 +148,13 @@ func startServer(
 		}
 	}()
 
-	rand.Seed(time.Now().UnixNano())
+	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
 
 	var ln net.Listener
 	const maxretry = 5
 	var retry int
 	for retry = 0; retry < maxretry; retry++ {
-		addr := "127.0.0.1:" + strconv.Itoa(minPort+rand.Intn(maxPort-minPort))
+		addr := "127.0.0.1:" + strconv.Itoa(minPort+rng.Intn(maxPort-minPort))
 		s.Addr = addr
 
 		ln, err = net.Listen("tcp", addr)

go.mod

@@ -1,6 +1,6 @@
 module github.com/terramate-io/terramate
 
-go 1.18
+go 1.20
 
 require (
 	github.com/alecthomas/kong v0.7.1