http://godoc.org?q=github.com/creachadair/goflags
The packages in this repository define extensions to the standard Go "flag"
package for additional types beyond the standard set, by providing
implementations of the flag.Value and
flag.Getter interfaces.
Defines a flag that accepts human-readable integer values, with shorthand for multiples of powers of 1024. For example, "1K" for 1024, "2.1m" for 2202009, and so forth.
Defines a flag that accepts a single string value taken from a fixed set of values chosen when the flag is defined. Values are compared without regard to case.
Defines a flag that accepts a valid
*regexp.Regexp
value compiled from a string literal.
Defines a flag that accepts a time.Time
value parsed via a standard format string.