| bytes | Package bytes implements functions for the manipulation of byte slices. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| go/token | Package token defines constants representing the lexical tokens of the Go programming language and basic operations on tokens (printing, predicates). |
| io | Package io provides basic interfaces to I/O primitives. |
| path/filepath | Package filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file 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. |
| unicode | Package unicode provides data and functions to test some properties of Unicode code points. |
| unicode/utf8 | Package utf8 implements functions and constants to support text encoded in UTF-8. |