I tried executing a function in the newest pre-release of 1.12, but have been unable to get a single successful run. I have attached the file I was trying to execute as a test, which was placed in a folder titled "folder" in the functions folder of my world. The command I used to try calling the function was /function folder:hi. As a note (don't know if this had a role in the error), my world has a "." in the name, which turned into a "_" in the name of the world folder. If this does have an effect on the performance of the function, I'll let you know after some brief testing.

UPDATE: After changing the world name, I confirmed that having a period in the world name has no effect on /function.