enhancement: added support for multiple subdomains

[mteiting]

This change should resolve #22 without introducing breaking changes for existing installations.

Multiple subdomains can be added now by adding new environment named variables.
Example:

RECORD_NAME_<NAME>=test
RECORD_NAME_<NAME>_TTL=600

RECORD_NAME_TEST1=test1
RECORD_NAME_TEST1_TTL=1440

RECORD_NAME_TEST2=test2
RECORD_NAME_TEST2_TTL=300

<NAME> does not need to match with the subdomain this is just an example.

Changes:

• Added support for multiple subdomains while maintaining support for single domains
• Changed fmt.Print* to log.Print* for logs with timestamp
• Changed ioutil.ReadAll to io.ReadAll since ioutil.ReadAll is deprecated

Remarks

• Failed to add test for testing single domain since it seems the same instance and variables cannot be added twice via flags
• Only works with environment variables

[kutzilla]

Thank you for the time to implement this long awaited feature. I got some improvements regarding the functionality determining a single- or multi-domain case. You're reading the environment variables by the prefix "RECORD_NAME" and if there are multiple env's starting with the prefix, you set the variable useDefaultConfig to false. In my opinion this is kind of problematic, because if you got env's with the same prefix, but maybe for different purposes, this could lead to an issue, because you cannot set this to multiple-subdomain-mode. In those cases an additional variable to set it in multiple-subdomain-mode could be very helpful. Therefore the determination of the mode is not dependent on the presence of certain variables. Something like MULTIPLE_DOMAIN_MODE=true would be a good name.

What do you think?

[mteiting]

The problem with this approach is, that recordConf.mode is only set after flags.Read().
So this would never be true during setup.

You would have to manually parse for MULTI_DOMAIN_MODE during setup.

While I understand the problem with the environment variable prefixing, I don't see variable shadowing being the problem here. You need to make a decision between going single or multi-domain. The advantage you'd have with MULTI_DOMAIN_MODE that it makes your choice clear when you opt either approach.

[kutzilla]

Valid point, I agree with you. This approach won't be helping, if the variable MULTI_DOMAIN_MODE is not read yet.