| 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/format | Package format implements standard formatting of Go source. |
| 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. |
| golang.org/x/sys/execabs | Package execabs is a drop-in replacement for os/exec that requires PATH lookups to find absolute paths. |
| golang.org/x/tools/go/packages | Package packages loads Go packages for inspection and analysis. |
| golang.org/x/tools/refactor/eg | Package eg implements the example-based refactoring tool whose command-line is defined in golang.org/x/tools/cmd/eg. |
| io/ioutil | Package ioutil implements some I/O utility functions. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| path/filepath | Package filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file paths. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |