| encoding | Package encoding defines interfaces shared by other packages that convert data to and from byte-level and textual representations. |
| 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. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| reflect | Package reflect implements run-time reflection, allowing a program to manipulate objects with arbitrary types. |
| regexp | Package regexp implements regular expression search. |
| 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. |
| text/tabwriter | Package tabwriter implements a write filter (tabwriter.Writer) that translates tabbed columns in input into properly aligned text. |
| text/template | Package template implements data-driven templates for generating textual output. |
| time | Package time provides functionality for measuring and displaying time. |