Middleware return early

[anthhub]

I want to add an 'end()' function to provide an option, it's able to backtrack previous middleware for early return.

[codecov[bot]]

Codecov Report

Merging #113 (00f1528) into master (25568a3) will not change coverage. The diff coverage is 100.00%.

:exclamation: Current head 00f1528 differs from pull request most recent head 8157e53. Consider uploading reports for the commit 8157e53 to get more accurate results

@@            Coverage Diff            @@
##            master      #113   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           15        19    +4     
  Branches         5         6    +1     
=========================================
+ Hits            15        19    +4     

Impacted Files	Coverage Δ
index.js	100.00% <100.00%> (ø)

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[jonathanong]

why?