go-tagexpr VS expr

Hertz uses the open-source library go-tagexpr for parameter binding and validation, which the current demo uses for user registration and login.

You may refer to here for more information about parameter validation syntax.

The go-tagexpr open source library is used for parameter binding and validation of the Field annotation, as shown in the following example for CreateUserRequest:

Uses the [expr](https://github.com/antonmedv/expr) language to achieve this and I've been super happy with the results.

I have been using expr (https://github.com/antonmedv/expr) to do something like this for a while. no complains so far.

If you wanted it to not require putting in the operation first and just accept string equations (without using something like https://github.com/antonmedv/expr) you could parse, tokenize and then process the input.

https://github.com/antonmedv/expr/ Seems really promising though having a rough time finding examples or basic do something as simple as struct.Value == N though I did find some examples on iterating and such.

https://github.com/antonmedv/expr for embedded expressions.

I think a number of people use the expr expression language, but I don't know how much functionality it has and how much you need. https://github.com/antonmedv/expr

We use https://github.com/antonmedv/expr at some other place for similar case, but there rules are bit simpler and this library seem to suit ideally for such simple "one line" conditions.