Go "missing return at end of function" - Fix in CI

By Kaveh Alemi·Latchkey

A function declaring a return value must end every reachable path with a return (or a terminating statement). Go rejects a function whose end is reachable without one.

What this error means

A build fails with missing return at end of function. It typically appears when a switch or if/else covers the expected cases but Go cannot prove the end is unreachable.

./classify.go:14:1: missing return at end of function

Common causes

A code path falls through without returning

An if/else or switch handles known cases but leaves the function end reachable without a return.

No default in an exhaustive-looking switch

Go does not treat a switch without default as exhaustive, so the function can reach its end.

How to fix it

Add a terminating return

1. Return a sensible value or error at the end of the function.
2. Or add a default branch that returns or panics.

default:
	return fmt.Errorf("unhandled case: %v", x)

Panic on truly unreachable paths

1. If the end really cannot be reached, make that explicit with a panic.

panic("unreachable")

How to prevent it

• Always cover the function end with a return or terminating statement.
• Add default branches to switches that produce a value.
• Build locally to catch missing returns before CI.

Frequently asked questions

Related guides

References

• Go documentation
• GitHub Actions documentation