| 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/build | Package build gathers information about 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). |
| golang.org/x/tools/go/buildutil | Package buildutil provides utilities related to the go/build package in the standard library. |
| golang.org/x/tools/go/loader | Package loader loads a complete Go program from source code, parsing and type-checking the initial packages plus their transitive closure of dependencies. |
| 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. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| os/exec | Package exec runs external commands. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |