Update supported go versions

Following our policy regarding supported go releases, change the
supported go versions to 1.19.* and 1.20.* with the release of go 1.20.
diff --git a/test/go/go.mod b/test/go/go.mod
index 841c329..0143eba 100644
--- a/test/go/go.mod
+++ b/test/go/go.mod
@@ -1,6 +1,6 @@
 module github.com/apache/thrift/test/go
 
-go 1.18
+go 1.19
 
 require (
 	github.com/apache/thrift v0.0.0-00010101000000-000000000000