Since nknd v2.0.6, build nkn node from src code required Golang v1.13 or above.
We have updated the GCP Marketplace image. But DO/AWS Marketplace image packaged golang still v1.12. (A long time routine for audit)
For a workaround (before passed DO/AWS Marketplace audit), You can follow the upgrade guide in v2.0.6 release notes to upgrade Golang.