Improve lexer package's code quality by fixing golint warnings.
Improve lexer package's code quality by fixing golint warnings.

st0012/Rooby,Maxwell-Alexius/goby,goby-lang/goby,goby-lang/goby,hachi8833/goby,hachi8833/goby,hachi8833/goby,goby-lang/goby,Maxwell-Alexius/goby,st0012/Rooby,Maxwell-Alexius/goby