Fix: Resolve problem of Block-scoped variable on cache code

[MichelRibeiro1]

When a method has one of these arguments: key, expirationSeconds, version, the build fails, due to a Block-scoped variable error.

[icaaro]

This bug is related with #35 issue

[icaaro]

My suggestion to solve this problem is rename the variable using _ since the sdkgen lang spec don't allow _ use in variable names, function declaration and etc . This way its impossible has a collision with this variable At least as long as the language specification does not change. iex _key.