Golang errors and such

errors.go

package main

// UserError contains error information presented to the users of our API
type UserError struct {
	Msg  string `json:"message"`
	Code int    `json:"error"`
}

// ApplicationError contains information about errors that arise while accessing resources.
type ApplicationError struct {
	Msg  string
	Err  error
	Code int
}

// Error returns a human-readable representation of a ApplicationError.
func (err *ApplicationError) Error() string {
	return err.Msg
}

// UserError return a user-facing error
func (rerr *ApplicationError) UserError() *UserError {
	return &UserError{Msg: rerr.Msg, Code: rerr.Code}
}

examples.go

// Just an application error, like a user who doesn't have permission to create another admin.
if !currentUser.IsAdmin() && u.IsAdmin() {
	return nil, &ApplicationError{Msg: "You must have admin privileges to create another admin user", Code: http.StatusForbidden}
}

// An actual error that occurs in our code. In this case, our crypto.
hash, herr := bcrypt.GenerateFromPassword([]byte(*u.Password), bcrypt.DefaultCost)
if herr != nil {
	return nil, &ApplicationError{Msg: "An unknown internal error has occured. This issue will be automatically reported.", Err: herr, Code: http.StatusInternalServerError}
}