| crypto | Package crypto collects common cryptographic constants. |
| errors | Package errors implements functions to manipulate errors. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| hash | Package hash provides interfaces for hash functions. |
| io | Package io provides basic interfaces to I/O primitives. |
| regexp | Package regexp implements regular expression search. |
| sort | Package sort provides primitives for sorting slices and user-defined collections. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |