Revert a change to removing some code

- This code is useful and this commit adds a comment to say why

authboss.go

@@ -35,16 +35,8 @@ func (a *Authboss) Init(modulesToLoad ...string) error {
 	}
 
 	for _, name := range modulesToLoad {
-		mod, ok := registeredModules[name]
+		if err := a.loadModule(name); err != nil {
-		if !ok {
+			return errors.Errorf("module %s failed to load", name)
-			return errors.Errorf("module %s was supposed to be loaded but is not registered", name)
-		}
-
-		a.loadedModules[name] = mod
-
-		// Initialize the module
-		if err := mod.Init(a); err != nil {
-			return errors.Wrapf(err, "failed to init module: %s", name)
 		}
 	}
 

module.go

@@ -1,5 +1,7 @@
 package authboss
 
+import "reflect"
+
 var registeredModules = make(map[string]Moduler)
 
 // Moduler should be implemented by all the authboss modules.
@@ -43,3 +45,38 @@ func (a *Authboss) IsLoaded(mod string) bool {
 	_, ok := a.loadedModules[mod]
 	return ok
 }
+
+// loadModule loads a particular module. It uses reflection to create a new
+// instance of the module type. The original value is copied, but not deep copied
+// so care should be taken to make sure most initialization happens inside the Initialize()
+// method of the module.
+//
+// This method exists so many copies of authboss can be loaded and initialized at the same time
+// if we didn't use this, then the registeredModules instances of the modules would end up used
+// by the first instance of authboss.
+func (a *Authboss) loadModule(name string) error {
+	module, ok := registeredModules[name]
+	if !ok {
+		panic("could not find module: " + name)
+	}
+
+	var wasPtr bool
+	modVal := reflect.ValueOf(module)
+	if modVal.Kind() == reflect.Ptr {
+		wasPtr = true
+		modVal = modVal.Elem()
+	}
+
+	modType := modVal.Type()
+	value := reflect.New(modType)
+	if !wasPtr {
+		value = value.Elem()
+		value.Set(modVal)
+	} else {
+		value.Elem().Set(modVal)
+	}
+
+	mod, ok := value.Interface().(Moduler)
+	a.loadedModules[name] = mod
+	return mod.Init(a)
+}