| errors | Package errors implements functions to manipulate errors. |
| flag | Package flag implements command-line flag parsing. |
| 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/build | Package build gathers information about Go packages. |
| go/token | Package token defines constants representing the lexical tokens of the Go programming language and basic operations on tokens (printing, predicates). |
| golang.org/x/tools/go/analysis | Package analysis defines the interface between a modular static analysis and an analysis driver program. |
| 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. |