Increasing local test stability (#1357)

* testing: increase local run reliability - using a SimpleRetryPolicy in createTable() makes my local testing runs much more reliable.
* mod: go 1.13 mod file to avoid continuous changes

common_test.go

@@ -59,7 +59,7 @@ func createTable(s *Session, table string) error {
 		return err
 	}
 
-	if err := s.Query(table).RetryPolicy(nil).Exec(); err != nil {
+	if err := s.Query(table).RetryPolicy(&SimpleRetryPolicy{}).Exec(); err != nil {
 		log.Printf("error creating table table=%q err=%v\n", table, err)
 		return err
 	}

go.mod

@@ -9,3 +9,5 @@ require (
 	github.com/stretchr/testify v1.3.0 // indirect
 	gopkg.in/inf.v0 v0.9.1
 )
+
+go 1.13