tests: added select_exists test for pgx

Author: victoraugustolls

internal/endtoend/testdata/select_exists/pgx/go/db.go

@@ -0,0 +1,13 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "driver": "pgx/v4",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql"
+    }
+  ]
+}

internal/endtoend/testdata/select_exists/go/models.go renamed to internal/endtoend/testdata/select_exists/pgx/go/models.go

@@ -0,0 +1,12 @@
+CREATE TABLE bar (id serial not null);
+
+-- name: BarExists :one
+SELECT
+    EXISTS (
+        SELECT
+            1
+        FROM
+            bar
+        where
+            id = $1
+    );