Because sometime your need a big alphanumeric string in Crystal

rand_str.cr

def rand_str(length = 16, supplemental_chars = "")
  res = [] of Char
  chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" + supplemental_chars
  length.times do { |i| res << chars[rand(chars.size)] }
  res.join()
end

rand_str 32
#=> xkURIpYnqbRVj893pr23LhhxeukFTu5f
  
# more characters can be used using the 2nd arg
rand_str 48, "!@#$%^&*"
#=> !JzRCOtU%Xr38c*Un$bS3VZygDIfo4lFK#F@^TZAtd8I6QSG