What Happens to the Return Values of Functions in Go Goroutines?

Return Value's Fate in Goroutines

In Go, goroutines are lightweight threads that execute concurrently. One common question arises when using goroutines—what happens to the return values of functions invoked within them?

Storage of Return Values

Contrary to popular belief, the return values of functions called from goroutines are stored on the stack. This is evident from assembly output, as demonstrated below:

go build -gcflags -S z.go

"".getNumber+0(SB)
MOVQ    "".i+8(FP),BX
MOVQ    BX,"".~r1+16(FP)

However, this stack is unique to the goroutine and is destroyed upon its completion, making the return values inaccessible to the main routine.

Retrieving Return Values

Despite being stored, the return values cannot be retrieved due to the isolation of goroutine stacks. This limitation emphasizes the importance of using alternative communication mechanisms such as channels to exchange information between goroutines and the main routine.

Avoidance of Return Values

Given the inaccessibility of return values, it's advisable to avoid using them in goroutines. Instead, consider leveraging channels for data exchange, ensuring reliable communication and value sharing.

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