| 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. |
| io/fs | Package fs defines basic interfaces to a file system. |
| io/ioutil | Package ioutil implements some I/O utility functions. |
| path | Package path implements utility routines for manipulating slash-separated paths. |
| reflect | Package reflect implements run-time reflection, allowing a program to manipulate objects with arbitrary types. |
| sort | Package sort provides primitives for sorting slices and user-defined collections. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| testing/iotest | Package iotest implements Readers and Writers useful mainly for testing. |
| time | Package time provides functionality for measuring and displaying time. |