Not OP, but Go has some major advantages in cryptography:
1. Well-supported standard libraries generally written by Google
2. Major projects like Vault and K8s that use those implementations and publish new stuff
3. Primary client language for many blockchains, bringing cryptography contributions from the likes of Ethereum Foundation, Tendermint, Algorand, ZK rollups, etc
4. The community seems to have realized that untangling the mess that is building C/C++ stuff is a fool's errand and seems to mostly prefer to reimplement it in Go
"The best" is still a strong claim. How does it stack up against Java or C#, for example?
Do you mean “best support for cryptography in the standard library”?
Because there is tremendous support for cryptography in, say, the C/C++ ecosystem, which has traditionally been the default language of cryptographers.