| 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/ast | Package ast declares the types used to represent syntax trees for Go packages. |
| go/doc | Package doc extracts source code documentation from a Go AST. |
| go/format | Package format implements standard formatting of Go source. |
| go/printer | Package printer implements printing of AST nodes. |
| go/scanner | Package scanner implements a scanner for Go source text. |
| go/token | Package token defines constants representing the lexical tokens of the Go programming language and basic operations on tokens (printing, predicates). |
| 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. |