add concurrency 5 & 6 archives

Author: steevehook

Diff for: archives/README.md

@@ -8,5 +8,7 @@ individual lesson:
 - [Concurrency in Go #2 - WaitGroups (Part 1)](https://youtu.be/srb6fbioEY4) - [[Download Zip]](https://github.com/golang-basics/concurrency/raw/master/archives/concurrency-2.tar.gz)
 - [Concurrency in Go #3 - WaitGroups (Part 2)](https://youtu.be/zAMUKb6fCO0) - [[Download Zip]](https://github.com/golang-basics/concurrency/raw/master/archives/concurrency-3.tar.gz)
 - [Concurrency in Go #4 - WaitGroups (Part 3)](https://youtu.be/_QNcn7LAANY) - [[Download Zip]](https://github.com/golang-basics/concurrency/raw/master/archives/concurrency-4.tar.gz)
+- [Concurrency in Go #5 - Atomics (Part 1)](https://youtu.be/nVjAS0uEnVM) - [[Download Zip]](https://github.com/golang-basics/concurrency/raw/master/archives/concurrency-5.tar.gz)
+- [Concurrency in Go #6 - Atomics (Part 2)](https://youtu.be/lKds8lAzt6s) - [[Download Zip]](https://github.com/golang-basics/concurrency/raw/master/archives/concurrency-6.tar.gz)
 
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