variable name syntax
A variable name must start with a letter or an underscore
character (_) A variable name cannot start with a digit.
A variable name can only contain alpha-numeric characters
and underscores ( a-z, A-Z , 0-9 , and _ ) Variable names
are case-sensitive (age, Age and AGE are three different
variables)
Source: W3Schools at 'https://www.w3schools.com/go/go_variable_naming_rules.php#:~:text=A%20variable%20name%20must%20start,AGE%20are%20three%20different%20variables)'