As suggested by @mmcloughlin we can move sign/dilithium/internal/ntt_amd64_src.go to sign/dilithium/internal/asm/ntt_amd64_src.go, sign/dilithium/internal/asm/go.mod and let it generate into its parent folder. This will prevent avo from ending up in the top-level go.mod file. However, at the moment avo guesses the name of the package to use in its stubs file by the name of the folder, so it will create a conflicting package asm directive. To fix this we would need to use asm/internal instead of asm or wait for mmcloughlin/avo#147 to be resolved.

(As a workaround we go mod tidy after a go generate.)