FlagToEnv converts flag string to upper-case environment variable key string.

NewStringsFlag creates a new string flag for which any one of the given strings is a valid value, and any other value is an error.

SetFlagsFromEnv parses all registered flags in the given flagset, and if they are not already set it attempts to set their values from environment variables.

SetPflagsFromEnv is similar to SetFlagsFromEnv.

URLsFromFlag returns a slices from url got from the flag.

DeprecatedFlag encapsulates a flag that may have been previously valid but is now deprecated.

IgnoredFlag encapsulates a flag that may have been previously valid but is now ignored.

StringsFlag implements the flag.Value interface.