v1.16.0

This version will only work with go1.16 and above.

BREAKING CHANGES
The io/ioutil package has been removed from 1.16, and all references updated.

• https://golang.org/doc/go1.16#ioutil

FEATURES ADDED
The new Func() function allows registering a flag implemented by calling a function, as a lighter-weight alternative to implementing the Value interface.

• https://golang.org/doc/go1.16#flag
• https://golang.org/pkg/flag/#Func