codegen: fix fk checking lambda producing non-lint-passing code

pkg/codegen/modelgenerate/generate_model.go

@@ -200,7 +200,7 @@ func buildFKCheckLambda(tbl schema.Table) (*ast.AssignStmt, bool) {
 								ret = append(ret, &ast.IfStmt{
 									Init: &ast.AssignStmt{
 										Lhs: []ast.Expr{ast.NewIdent("err")},
-										Tok: token.ASSIGN,
+										Tok: token.DEFINE,
 										Rhs: []ast.Expr{
 											&ast.CallExpr{
 												Fun: &ast.SelectorExpr{X: dbDB, Sel: ast.NewIdent("Get")},