| 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/parser | Package parser implements a parser for Go source files. |
| go/printer | Package printer implements printing of AST nodes. |
| go/token | Package token defines constants representing the lexical tokens of the Go programming language and basic operations on tokens (printing, predicates). |
| internal/format | |
| io | Package io provides basic interfaces to I/O primitives. |