OK, now that we know that this is a change that you want to affect all users, then a global or preferably a module-level variable or a property on a module-shared object would be fine.
If you want this change to be persistent and survive a server restart, then you would need to write the change to disk somewhere and have code that reads that setting back in from disk when your server restarts. A simple way to do that might be to read/write it to a file in the JSON format. That gives you simple extensibility to also include other settings in that file.
Your admin form can then just update this variable and trigger a save to disk of all the current settings.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…