v2: validator for `golang-jwt/jwt`

[oxisto]

https://github.com/golang-jwt/jwt will serve as a long-term replacement to https://github.com/dgrijalva/jwt-go. Following the ideas discussed in #73, I have added a validator that uses the new repository.

It follows largely the same style as the jose one, with a few exceptions:

• Clock skew is not supported
• Expected claims can not be set

I want to hold of on marking this "ready" until there is a first v3.2.1 release of https://github.com/golang-jwt/jwt, which will happened soon.

Additionally, it would probably make sense to put the validators in their own go module, so that only the validators have a dependency to the actual jwt libraries, not the middleware itself.

[grounded042]

Hey @oxisto thanks for this! I'm a little swamped at the moment, but I'm carving out some time on Friday to review this.

[codecov-commenter]

Codecov Report

Merging #91 (fe44742) into v2 (665e7da) will increase coverage by 1.85%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##               v2      #91      +/-   ##
==========================================
+ Coverage   90.56%   92.42%   +1.85%     
==========================================
  Files           2        3       +1     
  Lines         106      132      +26     
==========================================
+ Hits           96      122      +26     
  Misses          9        9              
  Partials        1        1              

Impacted Files	Coverage Δ
validate/jwt-go/jwtgo.go	100.00% <100.00%> (ø)

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[oxisto]

Overall this looks great and thank you for the contribution! I left a couple of comments and nits on cleanups.

It follows largely the same style as the jose one, with a few exceptions:

• Clock skew is not supported
• Expected claims can not be set

Not supporting clock skew isn't a blocker, but it is a downside here. One of the features we want to support is clock skew. Is it possible that golang-jwt/jwt will support this in the future?

Not supporting expected claims is no problem as that's a setup from the other package.

Thanks for the review, I will look at the smaller changes. I am planning to add clock skew among other validation features from the old v4 to golang-jwt/jwt in a backwards compatible way (see https://github.com/golang-jwt/jwt/issues/16). Unfortunately, I do not have a dedicate time-frame for this, yet. June is quite busy here.

[grounded042]

Awesome! Knowing it's on the backlock is a big help!