Hello. Actually, there is no technical difference between percussion instruments and keyboard instruments from a midi standpoint.
When you hit the pad of your percussion instrument, there are a few miliseconds in which your drumstick is in contact with its surface, and this is enough to trigger a midi note off event once the drumstick abandons the aforementioned surface of the pad. Plus, there are situations when the musician keeps the drumstick in touch with the pad for few seconds.
What you say about the ADSR of the instrument is true, Banibrata, as long as you are talking about the sound generator part of the instrument.
In percussion instruments, though, the most common way to set up this ADSR is a very short attack, if not zero, sustain zero and decay and release adjusted to the same value, being this a short one always.
Sustain zero makes the sound go even if you keep your drumstick in contact with the pad when you hit it, as percussion instruments do.
Decay is the time it will take for the sound to go in this scenario.
When you hit and release the pad immediately, which is the most common case, «release» is the time it will take for the sound to go, once the drumstick has left the pad. When you set both «decay» and «release» to the same value, being this a rather short one, this will give you the effect you are looking for.
Now, if you feel playful, you could set «decay» to an slightly shorter value than «release», so you can get a sort of «mute» effect that occur on drums when you leave your drumstick still touching the pad briefly, as opposed to the open sound that you get when you release the pad immediately.
Hope it helps.