I think to keep Go code directly callable from C, they have to follow the platform's C calling conventions which means the same stack layout. So for cooperative

I think to keep Go code directly callable from C, they have to follow the platform's C calling conventions which means the same stack layout. So for cooperative concurrency on a single thread to work, each Goroutine needs its very own stack. On Intel, that means saving stack pointers RSP and RBP (16 bytes) for each. Also, each will need memory allocated for its stack for the stack pointers to point to... another 8-16 bytes (pointer and length).