There could have been a data race in your code with the usage of allMax
variable which is updated and checked by multiple goroutines. But you are
saved by the use of mutex. All shared variables, in general, are subject to
data races when there is a write involved. The local variables you create
Reading only is safe, but you will have a data race if two goroutines
access the same variable concurrently and at least one of the accesses is a
write. Here is an article that gives some rules of thumb on how to
efficiently schedule parallel computation on separate CPUs:
http://yourbasic.org/g
When you have such questions, then run your code with the race
detector. https://golang.org/doc/articles/race_detector.html
Otherwise, you are only reading from the slice, there is no racing possible.
Also, your max function looks very weird and has a small bug:
https://play.golang.org/p/8K-0ze3
