Update linting

* Move errcheck exclude list to config file.
* Enable revive linter
* Fix up revive linting issues.

Signed-off-by: SuperQ <superq@gmail.com>

cmd/postgres_exporter/main.go

@@ -34,7 +34,7 @@ import (
 )
 
 var (
-	c = config.ConfigHandler{
+	c = config.Handler{
 		Config: &config.Config{},
 	}