How Stack vs Heap Allocation Works in Go

Go uses escape analysis at compile time to decide if a variable lives on the stack (fast, automatic cleanup) or the heap (managed by the garbage collector). If a variable's lifetime extends beyond the function scope (e.g., returned by reference or stored in a global), it escapes to the heap; otherwise, it stays on the stack. You can inspect this behavior using the compiler flag -gcflags=-m.

go build -gcflags=-m -gcflags=-m your_program.go

The output will list variables and explicitly state escapes to heap or does not escape.

Think of the stack as a temporary workspace for variables that only exist while a function is running, and the heap as long-term storage for data that needs to survive after the function finishes. Go automatically moves data to the heap only when necessary, keeping your program fast by default. This happens behind the scenes so you don't have to manage memory manually.