Expected Behavior

To use Substitution field in TextMessageV2 should be able to use any of the substition type.

Current Behavior

Cannot use any of the substitions type (eg. MentionSubstitutionObject) as value in map of Substitution to push message.

Fix

Change type of Substitution from map[string]SubstitutionObject to map[string]SubstitutionObjectInterface in File: linebot/messaging_api/model_text_message_v2.go Line: 50 (or wherever it's defined) seems to fixed the issue.