Function randi 

pub fn randi() -> i64

Returns a random unsigned 32-bit integer. Use remainder to obtain a random value in the interval [0, N - 1] (where N is smaller than 2^32).

randi()           # Returns random integer between 0 and 2^32 - 1
randi() % 20      # Returns random integer between 0 and 19
randi() % 100     # Returns random integer between 0 and 99
randi() % 100 + 1 # Returns random integer between 1 and 100