Please explain this code (channels)

I can't understand howcome only the loop part of total() function being run 3 times not the whole function. res := 0 runs only once while range part runs 3 times. My background is in Python and Java and the way total function is run not making sense at all.

http://pastebin.com/4fEvfGsU

Because range on channel blocks if there is nothing to receive. You need to learn about channels in Go.

Read up on channels and goprocs. You have started a background function (total()), which is going to read from channel in, adding to res until in is closed.  Then the for loop end and the result is sent on the out channel back to main

total is NOT run three times.