Upgrade pgx driver, close #139

Author: jinzhu

go.mod

@@ -3,7 +3,7 @@ module gorm.io/driver/postgres
 go 1.14
 
 require (
-	github.com/jackc/pgx/v4 v4.17.2
+	github.com/jackc/pgx/v5 v5.0.4
 	github.com/jinzhu/now v1.1.5 // indirect
 	golang.org/x/crypto v0.1.0 // indirect
 	gorm.io/gorm v1.24.1