Shutter Speed isn’t really a concept that translates to a real time rendered 3d environment. As I’m sure you’re aware if you’re asking this, the idea behind shutter speed is that you control the amount of time a frame is exposed for and will lead to more/less light and also more/less motion blur.
In a game engine everything is on a fixed delta time, that being however many milliseconds there are between each frame. In the project settings you can set a fixed frame rate, to 24 or whatever you want, however if there’s any controller input from the player this will feel bad and it probably still won’t give you the results you want.
What effect are you trying to achieve by changing the shutter speed? If it is just a more film like appearance your best bet is to play with the motion blur in the rendering features of the camera itself.
If that isn’t what you want to change it for, let me know what you are trying to achieve and I’ll try and help you come up with a solution to what you are trying to achieve.