| errors | Package errors implements functions to manipulate errors. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| net/url | Package url parses URLs and implements query escaping. |
| path | Package path implements utility routines for manipulating slash-separated paths. |
| 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. |