This is a tiny go script that just generates a single, 256-bit bip39 mnemonic from a cryptographic randomness source. It's a tiny executable wrapper around the github.com/tyler-smith/go-bip39 package.
If you're looking for a CLI tool with more than one feature, you probably want the bip39 tool over here: https://github.com/kubetrail/bip39
Installation and usage
Installation and usage are pretty simple though. Assuming no familiarity with standard module handling in go: