Update store interface implementation

Author: Keda87

go.mod

@@ -3,14 +3,9 @@ module github.com/go-oauth2/mysql
 go 1.14
 
 require (
-	github.com/go-gorp/gorp v2.2.0+incompatible // indirect
 	github.com/go-oauth2/oauth2/v4 v4.1.1
 	github.com/go-sql-driver/mysql v1.5.0
 	github.com/json-iterator/go v1.1.10
-	github.com/lib/pq v1.7.0 // indirect
-	github.com/mattn/go-sqlite3 v1.14.0 // indirect
-	github.com/poy/onpar v1.0.0 // indirect
 	github.com/smartystreets/goconvey v1.6.4
-	github.com/ziutek/mymysql v1.5.4 // indirect
 	gopkg.in/gorp.v2 v2.2.0
 )