| bytes | Package bytes implements functions for the manipulation of byte slices. |
| crypto | Package crypto collects common cryptographic constants. |
| crypto/rand | Package rand implements a cryptographically secure random number generator. |
| crypto/subtle | Package subtle implements functions that are often useful in cryptographic code but require careful thought to use correctly. |
| errors | Package errors implements functions to manipulate errors. |
| hash | Package hash provides interfaces for hash functions. |
| io | Package io provides basic interfaces to I/O primitives. |
| math | Package math provides basic constants and mathematical functions. |
| math/big | Package big implements arbitrary-precision arithmetic (big numbers). |