Support multiple ENV variables

[shellbear]

It would be useful to support multiple ENV variables at once separated by commas.

Example:

type Example struct {
    Port int `env:"APPLICATION_PORT,PORT" default:"8080"`
}

So use can provide the port argument with multiple environment variables.

Thank you.

[alecthomas]

I agree this would be useful.

[alecthomas]

This is supported now.