| bytes | Package bytes implements functions for the manipulation of byte slices. |
| go/ast | Package ast declares the types used to represent syntax trees for Go packages. |
| go/format | Package format implements standard formatting of Go source. |
| go/importer | Package importer provides access to export data importers. |
| go/parser | Package parser implements a parser for Go source files. |
| go/token | Package token defines constants representing the lexical tokens of the Go programming language and basic operations on tokens (printing, predicates). |
| go/types | Package types declares the data types and implements the algorithms for type-checking of Go packages. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |