I met error when get Channel Subscribers

Yes, I know.

user.username variable is same with channel_id.

My channel url is ‘https://www.twitch.tv/poXXXXX’.
And, My display name is poXXXXX.
And user.username variable is displayname.

And, I checked it through this below.
fetch(‘https://api.twitch.tv/kraken/channels/<%=user.username%>’,

Is my opinion correct?