(The articles are annotated with publication date. That's because Go internals change from time to time, so older writeups have higher risk of becoming obsolete with time.)

• 2013.09.08 The Go netpoller. A short, high-level overview.
• 2013.06.30 The Go scheduler. Has pretty pictures!
• 2013.06.02 Why is a Goroutine's stack infinite? On [“split stacks”].
• 2011.02.15 A trip down the (split) rabbithole. On split stacks.
• (2011.02.07) Split Stacks in GCC. On split stacks, by Ian Lance Taylor (one of the core Go developers).
• 2009.11.24 Go Data Structures. By Russ Cox (one of Go authors).
• go-wiki/DesignDocuments – contains some detailed proposals for various past and future reworkings of Go internals.