| encoding/json | Package json implements encoding and decoding of JSON as defined in RFC 7159. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| github.com/coreos/etcd/error | error package describes errors in etcd project. |
| math/rand | Package rand implements pseudo-random number generators suitable for tasks such as simulation, but it should not be used for security-sensitive work. |
| path | Package path implements utility routines for manipulating slash-separated paths. |
| sort | Package sort provides primitives for sorting slices and user-defined collections. |
| strconv | Package strconv implements conversions to and from string representations of basic data types. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |
| time | Package time provides functionality for measuring and displaying time. |