Simple introsort implementation with concurrency.
$ go get -u github.com/heistp/introsort
$ introsort
number of elements: 10485760
sorted successfully: true
concurrent sort: false
elapsed: 876.480542ms
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number of elements: 10485760
sorted successfully: true
concurrent sort: true
elapsed: 237.963062ms
-----
cores: 6
concurrency speedup: 3.683