| encoding | Package encoding defines interfaces shared by other packages that convert data to and from byte-level and textual representations. |
| encoding/binary | Package binary implements simple translation between numbers and byte sequences and encoding and decoding of varints. |
| errors | Package errors implements functions to manipulate errors. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| io | Package io provides basic interfaces to I/O primitives. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |